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Merge pull request #4002 from sivaprasath2004/sivaprasath-closes-issue-3958
246. Strobogrammatic Number
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‎dsa-solutions/lc-solutions/0200-0299/0246-Strobogrammatic-Number.md

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---
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id: strobogrammatic-number
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title: Strobogrammatic Number
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sidebar_label: 0246-Strobogrammatic Number
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tags: [Hash Map, Two Pointers]
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description: Solution to finding the Strobogrammatic Number in an array of strings.
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---
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### Description
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A strobogrammatic number is a number that looks the same when rotated 180 degrees (looked at upside down).
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Write a function to determine if a number is strobogrammatic. The number is represented as a string.
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### Example:
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**Example 1:**
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```bash
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Input: "69"
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Output: true
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```
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**Example 2:**
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```bash
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Input: "88"
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Output: true
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```
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**Example 3:**
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```bash
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Input: "962"
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Output: false
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```
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### Solution
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#### Approach
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1. Create a dictionary to map each digit to its strobogrammatic counterpart.
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2. Iterate over the number from both ends towards the center.
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3. For each pair of digits, check if they are valid strobogrammatic pairs using the dictionary.
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4. Return true if all pairs are valid, otherwise return false.
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#### Codes in Different Languages
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<Tabs>
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<TabItem value="javascript" label="JavaScript">
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<SolutionAuthor name="@sivaprasath"/>
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```javascript
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function isStrobogrammatic(num) {
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const strobogrammaticMap = {
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'0': '0',
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'1': '1',
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'6': '9',
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'8': '8',
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'9': '6'
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};
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let left = 0, right = num.length - 1;
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while (left <= right) {
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if (!(num[left] in strobogrammaticMap) || strobogrammaticMap[num[left]] !== num[right]) {
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return false;
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}
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left++;
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right--;
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}
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return true;
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}
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// Example usage:
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console.log(isStrobogrammatic("69")); // Output: true
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console.log(isStrobogrammatic("88")); // Output: true
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console.log(isStrobogrammatic("962")); // Output: false
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```
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</TabItem>
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<TabItem value="typescript" label="TypeScript">
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<SolutionAuthor name="@sivaprasath"/>
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```typescript
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function isStrobogrammatic(num: string): boolean {
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const strobogrammaticMap: { [key: string]: string } = {
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'0': '0',
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'1': '1',
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'6': '9',
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'8': '8',
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'9': '6'
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};
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let left = 0, right = num.length - 1;
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while (left <= right) {
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if (!(num[left] in strobogrammaticMap) || strobogrammaticMap[num[left]] !== num[right]) {
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return false;
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}
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left++;
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right--;
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}
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return true;
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}
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// Example usage:
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console.log(isStrobogrammatic("69")); // Output: true
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console.log(isStrobogrammatic("88")); // Output: true
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console.log(isStrobogrammatic("962")); // Output: false
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```
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</TabItem>
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<TabItem value="python" label="Python">
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<SolutionAuthor name="@sivaprasath"/>
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```python
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def isStrobogrammatic(num):
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strobogrammatic_map = {'0': '0', '1': '1', '6': '9', '8': '8', '9': '6'}
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left, right = 0, len(num) - 1
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while left <= right:
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if num[left] not in strobogrammatic_map or strobogrammatic_map[num[left]] != num[right]:
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return False
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left += 1
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right -= 1
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return True
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# Example usage:
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print(isStrobogrammatic("69")) # Output: true
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print(isStrobogrammatic("88")) # Output: true
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print(isStrobogrammatic("962")) # Output: false
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```
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</TabItem>
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<TabItem value="java" label="Java">
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<SolutionAuthor name="@sivaprasath"/>
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```java
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import java.util.HashMap;
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import java.util.Map;
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public class StrobogrammaticNumber {
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public static boolean isStrobogrammatic(String num) {
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Map<Character, Character> strobogrammaticMap = new HashMap<>();
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strobogrammaticMap.put('0', '0');
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strobogrammaticMap.put('1', '1');
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strobogrammaticMap.put('6', '9');
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strobogrammaticMap.put('8', '8');
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strobogrammaticMap.put('9', '6');
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int left = 0, right = num.length() - 1;
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while (left <= right) {
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if (!strobogrammaticMap.containsKey(num.charAt(left)) || strobogrammaticMap.get(num.charAt(left)) != num.charAt(right)) {
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return false;
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}
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left++;
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right--;
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}
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return true;
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}
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public static void main(String[] args) {
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System.out.println(isStrobogrammatic("69")); // Output: true
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System.out.println(isStrobogrammatic("88")); // Output: true
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System.out.println(isStrobogrammatic("962")); // Output: false
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}
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}
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```
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</TabItem>
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<TabItem value="cpp" label="C++">
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<SolutionAuthor name="@sivaprasath"/>
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```cpp
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#include <iostream>
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#include <unordered_map>
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#include <string>
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using namespace std;
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bool isStrobogrammatic(string num) {
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unordered_map<char, char> strobogrammaticMap = {
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{'0', '0'},
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{'1', '1'},
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{'6', '9'},
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{'8', '8'},
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{'9', '6'}
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};
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int left = 0, right = num.length() - 1;
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while (left <= right) {
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if (strobogrammaticMap.find(num[left]) == strobogrammaticMap.end() || strobogrammaticMap[num[left]] != num[right]) {
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return false;
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}
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left++;
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right--;
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}
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return true;
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}
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int main() {
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cout << boolalpha;
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cout << isStrobogrammatic("69") << endl; // Output: true
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cout << isStrobogrammatic("88") << endl; // Output: true
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cout << isStrobogrammatic("962") << endl; // Output: false
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return 0;
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}
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```
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</TabItem>
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</Tabs>
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#### Explanation:
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<Tabs>
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<TabItem value="javascript" label="Javascript">
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1. The `strobogrammaticMap` defines the valid strobogrammatic pairs.
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2. Two pointers, `left` and `right`, traverse the string from both ends towards the center.
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3. For each pair of digits, we check if they exist in the map and match the required strobogrammatic counterpart.
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4. If any pair is invalid, return false; if all pairs are valid, return true.
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</TabItem>
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<TabItem value="typescript" label="TypeScript">
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1. The `strobogrammaticMap` defines the valid strobogrammatic pairs.
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2. Two pointers, `left` and `right`, traverse the string from both ends towards the center.
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3. For each pair of digits, we check if they exist in the map and match the required strobogrammatic counterpart.
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4. If any pair is invalid, return false; if all pairs are valid, return true.
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</TabItem>
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<TabItem value="python" label="Python">
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1. The dictionary `strobogrammatic_map` defines the valid strobogrammatic pairs.
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2. Two pointers, `left` and `right`, are used to traverse the number from both ends.
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3. For each pair of digits, we check if they are in the dictionary and match the required strobogrammatic counterpart.
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4. If any pair is invalid, return false; if all pairs are valid, return true.
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</TabItem>
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<TabItem value="java" label="Java">
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1. The `strobogrammaticMap` defines the valid strobogrammatic pairs.
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2. Two pointers, `left` and `right`, traverse the string from both ends towards the center.
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3. For each pair of digits, we check if they exist in the map and match the required strobogrammatic counterpart.
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4. If any pair is invalid, return false; if all pairs are valid, return true.
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</TabItem>
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<TabItem value="cpp" label="C++">
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1. The `strobogrammaticMap` defines the valid strobogrammatic pairs.
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2. Two pointers, `left` and `right`, traverse the string from both ends towards the center.
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3. For each pair of digits, we check if they exist in the map and match the required strobogrammatic counterpart.
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4. If any pair is invalid, return false; if all pairs are valid, return true.
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</TabItem>
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</Tabs>
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#### Complexity:
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<Tabs>
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<TabItem value="javascript" label="Javascript">
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1. **Time complexity**: $O(n)$, where $n$ is the length of the input string, as we only iterate through the string once.
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2. **Space complexity**: $O(1)$, as we use a fixed amount of extra space for the map and pointers.
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3. This makes the approach efficient and suitable for checking strobogrammatic properties in linear time.
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</TabItem>
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<TabItem value="typescript" label="TypeScript">
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1. **Time complexity**: $O(n)$, where $n$ is the length of the input string, as we only iterate through the string once.
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2. **Space complexity**: $O(1)$, as we use a fixed amount of extra space for the map and pointers.
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3. This makes the approach efficient and suitable for checking strobogrammatic properties in linear time.
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</TabItem>
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<TabItem value="python" label="Python">
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1. Time complexity: $O(n)$, where $n$ is the length of the input string, as we only iterate through the string once.
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2. Space complexity: $O(1)$, as we use a fixed amount of extra space for the dictionary and pointers.
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3. This makes the approach efficient and suitable for checking strobogrammatic properties in linear time.
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</TabItem>
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<TabItem value="java" label="Java">
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1. **Time complexity**: $O(n)$, where $n$ is the length of the input string, as we only iterate through the string once.
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2. **Space complexity**: $O(1)$, as we use a fixed amount of extra space for the map and pointers.
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3. This makes the approach efficient and suitable for checking strobogrammatic properties in linear time.
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</TabItem>
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<TabItem value="cpp" label="C++">
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1. **Time complexity**: $O(n)$, where $n$ is the length of the input string, as we only iterate through the string once.
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2. **Space complexity**: $O(1)$, as we use a fixed amount of extra space for the map and pointers.
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3. This makes the approach efficient and suitable for checking strobogrammatic properties in linear time.
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</TabItem>
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</Tabs>
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## References
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- **LeetCode Problem:** [Strobogrammatic Number](https://leetcode.com/problems/strobogrammatic-number/)
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<h2>Author:</h2>
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<div style={{display: 'flex', flexWrap: 'wrap', justifyContent: 'space-between', gap: '10px'}}>
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{['sivaprasath2004'].map(username => (
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<Author key={username} username={username} />
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))}
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</div>

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