Merge branch 'main' into patch-3

Author: ajay-dhangar

dsa-problems/leetcode-problems/0900-0999.md

@@ -111,7 +111,7 @@ export const problems = [
         problemName: "916. Word Subsets",
         difficulty: "Medium",
         leetCodeLink: "https://leetcode.com/problems/word-subsets",
-        solutionLink: "#"
+        solutionLink: "/dsa-solutions/lc-solutions/0900-0999/word-subsets"
     },
     {
         problemName: "917. Reverse Only Letters",

dsa-solutions/lc-solutions/0900-0999/0916-word-subsets.md

@@ -0,0 +1,195 @@
+---
+id: word-subsets
+title: Word Subsets
+sidebar_label: 0916 - Word Subsets
+tags:
+  - String
+  - Array
+  - Hash Table
+description: "This is a solution to the Word Subsets problem on LeetCode."
+---
+
+## Problem Description
+
+You are given two string arrays `words1` and `words2`.
+
+A string `b` is a **subset** of string `a` if every letter in `b` occurs in `a` including multiplicity.
+
+- For example, `"wrr"` is a subset of `"warrior"` but is not a subset of `"world"`.
+
+A string `a` from `words1` is **universal** if for every string `b` in `words2`, `b` is a subset of `a`.
+
+Return an array of all the **universal** strings in `words1`. You may return the answer in **any order**.
+
+### Examples
+
+**Example 1:**
+
+```
+Input: words1 = ["amazon","apple","facebook","google","leetcode"], words2 = ["e","o"]
+Output: ["facebook","google","leetcode"]
+```
+**Example 2:**
+
+```
+Input: words1 = ["amazon","apple","facebook","google","leetcode"], words2 = ["l","e"]
+Output: ["apple","google","leetcode"]
+```
+
+### Constraints
+
+- $1 \leq words1.length, words2.length \leq 10^4$
+- $1 \leq words1[i].length, words2[i].length \leq 10$
+- `words1[i]` and `words2[i]` consist only of lowercase English letters.
+- All the strings of `words1` are **unique**.
+
+## Solution for Word Subsets
+
+## Approach: Reduce to Single Word in B
+### Intuition
+
+If b is a subset of a, then say a is a superset of b. Also, say $(word)N_{\text{"a"}}(\text{word})$ is the count of the number of $\text{"a"}$'s in the word.
+
+When we check whether a word `wordA` in `A` is a superset of `wordB`, we are individually checking the counts of letters: that for each $\text{letter}$, we have $N_{\text{letter}}(\text{wordA}) \geq N_{\text{letter}}(\text{wordB})$.
+
+Now, if we check whether a word `wordA` is a superset of all words $\text{wordB}_i$, we will check for each letter and each i, that $N_{\text{letter}}(\text{wordA}) \geq N_{\text{letter}}(\text{wordB}_i)$. This is the same as checking $N_{\text{letter}}(\text{wordA}) \geq \max\limits_i(N_{\text{letter}}(\text{wordB}_i))$.
+
+For example, when checking whether `"warrior"` is a superset of words B = `["wrr", "wa", "or"]`, we can combine these words in `B` to form a "maximum" word `"arrow"`, that has the maximum count of every letter in each word in `B`.
+
+### Algorithm
+
+Reduce `B` to a single word `bmax` as described above, then compare the counts of letters between words `a` in `A`, and `bmax`.
+
+### Code in Different Languages
+
+<Tabs>
+<TabItem value="cpp" label="C++">
+  <SolutionAuthor name="@Shreyash3087"/>
+
+```cpp
+#include <vector>
+#include <string>
+#include <unordered_map>
+
+class Solution {
+public:
+    std::vector<std::string> wordSubsets(std::vector<std::string>& A, std::vector<std::string>& B) {
+        std::vector<int> bmax(26, 0);
+        for (const auto& b : B) {
+            std::unordered_map<char, int> bCount = count(b);
+            for (int i = 0; i < 26; ++i)
+                bmax[i] = std::max(bmax[i], bCount[static_cast<char>('a' + i)]);
+        }
+
+        std::vector<std::string> ans;
+        for (const auto& a : A) {
+            std::unordered_map<char, int> aCount = count(a);
+            bool universal = true;
+            for (int i = 0; i < 26; ++i) {
+                if (aCount[static_cast<char>('a' + i)] < bmax[i]) {
+                    universal = false;
+                    break;
+                }
+            }
+            if (universal)
+                ans.push_back(a);
+        }
+
+        return ans;
+    }
+
+private:
+    std::unordered_map<char, int> count(const std::string& S) {
+        std::unordered_map<char, int> ans;
+        for (char c : S)
+            ans[c]++;
+        return ans;
+    }
+};
+
+
+```
+</TabItem>
+<TabItem value="java" label="Java">
+  <SolutionAuthor name="@Shreyash3087"/>
+
+```java
+class Solution {
+    public List<String> wordSubsets(String[] A, String[] B) {
+        int[] bmax = count("");
+        for (String b: B) {
+            int[] bCount = count(b);
+            for (int i = 0; i < 26; ++i)
+                bmax[i] = Math.max(bmax[i], bCount[i]);
+        }
+
+        List<String> ans = new ArrayList();
+        search: for (String a: A) {
+            int[] aCount = count(a);
+            for (int i = 0; i < 26; ++i)
+                if (aCount[i] < bmax[i])
+                    continue search;
+            ans.add(a);
+        }
+
+        return ans;
+    }
+
+    public int[] count(String S) {
+        int[] ans = new int[26];
+        for (char c: S.toCharArray())
+            ans[c - 'a']++;
+        return ans;
+    }
+}
+```
+
+</TabItem>
+<TabItem value="python" label="Python">
+  <SolutionAuthor name="@Shreyash3087"/>
+
+```python
+class Solution(object):
+    def wordSubsets(self, A, B):
+        def count(word):
+            ans = [0] * 26
+            for letter in word:
+                ans[ord(letter) - ord('a')] += 1
+            return ans
+
+        bmax = [0] * 26
+        for b in B:
+            for i, c in enumerate(count(b)):
+                bmax[i] = max(bmax[i], c)
+
+        ans = []
+        for a in A:
+            if all(x >= y for x, y in zip(count(a), bmax)):
+                ans.append(a)
+        return ans
+```
+</TabItem>
+</Tabs>
+
+### Complexity Analysis
+
+#### Time Complexity: $O(\mathcal{A}+\mathcal{B})$
+
+> **Reason**: where $\mathcal{A}$ and $\mathcal{B}$ is the total amount of information in A and B respectively.
+
+#### Space Complexity: $O(A.length+B.length)$
+
+## Video Solution 
+
+<LiteYouTubeEmbed
+    id="ByQfvU8_fvM"
+    params="autoplay=1&autohide=1&showinfo=0&rel=0"
+    title="Word Subsets | Live Coding with Explanation | Leetcode - 916"
+    poster="hqdefault"
+    webp />
+
+## References
+
+- **LeetCode Problem**: [Word Subsets](https://leetcode.com/problems/word-subsets/description/)
+
+- **Solution Link**: [Word Subsets](https://leetcode.com/problems/word-subsets/solutions/)