Add a Solution for plus one (LeetCode Problem 66)

dsa-solutions/lc-solutions/0000-0099/0066-plus-one.md

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+---
+id: plus-one
+title: Plus One (LeetCode)
+difficulty: Easy
+sidebar_label: 0066-PlusOne
+topics:
+  - Array
+---
+
+## Problem Description
+
+| Problem Statement | Solution Link | LeetCode Profile |
+| :---------------- | :------------ | :--------------- |
+| [Merge Two Sorted Lists](https://leetcode.com/problems/plus-one/) | [Merge Two Sorted Lists Solution on LeetCode](https://leetcode.com/problems/plus-one/solutions/) |  [VijayShankerSharma](https://leetcode.com/u/darkknight648/) |
+
+## Problem Description
+
+You are given a large integer represented as an integer array `digits`, where each `digits[i]` is the ith digit of the integer. The digits are ordered from most significant to least significant in left-to-right order. The large integer does not contain any leading 0's.
+
+Increment the large integer by one and return the resulting array of digits.
+
+### Examples
+
+#### Example 1
+
+- **Input:** digits = [1,2,3]
+- **Output:** [1,2,4]
+- **Explanation:** The array represents the integer 123. Incrementing by one gives 123 + 1 = 124. Thus, the result should be [1,2,4].
+
+#### Example 2
+
+- **Input:** digits = [4,3,2,1]
+- **Output:** [4,3,2,2]
+- **Explanation:** The array represents the integer 4321. Incrementing by one gives 4321 + 1 = 4322. Thus, the result should be [4,3,2,2].
+
+#### Example 3
+
+- **Input:** digits = [9]
+- **Output:** [1,0]
+- **Explanation:** The array represents the integer 9. Incrementing by one gives 9 + 1 = 10. Thus, the result should be [1,0].
+
+### Constraints
+
+- `1 <= digits.length <= 100`
+- `0 <= digits[i] <= 9`
+- `digits` does not contain any leading 0's.
+
+### Approach
+
+To increment the large integer represented by the `digits` array, we can follow these steps:
+
+1. Start from the least significant digit.
+2. Increment the last digit by 1.
+3. If the last digit becomes 10 after incrementing, set it to 0 and carry over 1 to the next digit.
+4. Repeat this process until there's no carry left or we reach the most significant digit.
+5. If there's a carry left after processing all digits, insert it at the beginning of the `digits` array.
+
+### Solution Code
+
+#### Python
+
+```
+class Solution(object):
+    def plusOne(self, digits):
+        for i in range(len(digits) - 1, -1, -1):
+            if digits[i] < 9:
+                digits[i] += 1
+                return digits
+            digits[i] = 0
+        return [1] + digits
+```
+
+#### C++
+
+```
+class Solution {
+public:
+    vector<int> plusOne(vector<int>& digits) {
+        int n = digits.size();
+        int carry = 1;
+        for (int i = n - 1; i >= 0; --i) {
+            digits[i] += carry;
+            carry = digits[i] / 10;
+            digits[i] %= 10;
+        }
+        if (carry) {
+            digits.insert(digits.begin(), carry);
+        }
+        return digits;
+    }
+};
+```
+
+#### Java
+
+```
+class Solution {
+    public int[] plusOne(int[] digits) {
+        int n = digits.length;
+        int carry = 1;
+        for (int i = n - 1; i >= 0; --i) {
+            digits[i] += carry;
+            carry = digits[i] / 10;
+            digits[i] %= 10;
+        }
+        if (carry != 0) {
+            int[] result = new int[n + 1];
+            result[0] = carry;
+            for (int i = 1; i < n + 1; ++i) {
+                result[i] = digits[i - 1];
+            }
+            return result;
+        }
+        return digits;
+    }
+}
+```
+
+### Conclusion
+
+The "Plus One" problem can be efficiently solved by incrementing the large integer represented by the digits array by one. The provided solution code implements this approach in Python, C++, and Java, providing an optimal solution to the problem.