Minimum Window Substring

Author: ShyamMahajan

minimum-window-substring.js

@@ -0,0 +1,67 @@
+/**Given two strings s and t of lengths m and n respectively, return the minimum window substring of s such that every character in t (including duplicates) is included in the window. If there is no such substring, return the empty string "".
+
+The testcases will be generated such that the answer is unique.
+
+A substring is a contiguous sequence of characters within the string. */
+
+/**
+ * @param {string} s
+ * @param {string} t
+ * @return {string}
+ */
+ var minWindow = function(s, t) {
+    const map = new Map()
+    for (let i = 0; i < t.length; i++) {
+      map.set(t[i], (map.get(t[i]) || 0) + 1)
+    }
+  
+    let count = 1
+    let start = 0
+    while (start < s.length && !map.has(s[start])) {
+      start++
+    }
+    if (start === s.length) {
+      return ''
+    }
+    if (t.length === 1) {
+      return s[start]
+    }
+    map.set(s[start], map.get(s[start]) - 1)
+  
+    let minStart = start
+    let minEnd = s.length
+  
+    for (end = start + 1; end < s.length; end++) {
+      if (map.has(s[end])) {
+        let endCount = map.get(s[end])
+        map.set(s[end], --endCount)
+        // endCount < 0 means there are too many s[end] within the window.
+        if (endCount >= 0) {
+          count++
+        }
+  
+        // There could be too may s[start] within the window.
+        // So after dumping the first s[start] the window might still be full.
+        while (count === t.length) {
+          if (end - start < minEnd - minStart) {
+            minStart = start
+            minEnd = end
+          }
+  
+          let startCount = map.get(s[start])
+          map.set(s[start], ++startCount)
+          if (startCount > 0) {
+            // the window is not full anymore
+            count--
+          }
+  
+          start++
+          while (!map.has(s[start])) {
+            start++
+          }
+        }
+      }
+    }
+  
+    return minEnd === s.length ? '' : s.slice(minStart, minEnd + 1)
+  };

readme.md

@@ -18,4 +18,5 @@
 14. Search in Rotated Sorted Array - (https://leetcode.com/problems/search-in-rotated-sorted-array/)
 15. 3Sum - (https://leetcode.com/problems/3sum/)
 16. Container With Most Water - (https://leetcode.com/problems/container-with-most-water/)
-17. Longest Substring Without Repeating Characters - (https://leetcode.com/problems/longest-substring-without-repeating-characters/)
+17. Longest Substring Without Repeating Characters - (https://leetcode.com/problems/longest-substring-without-repeating-characters/)
+18. Minimum Window Substring - (https://leetcode.com/problems/minimum-window-substring/)