Minimum_Window_Substring.js

Author: ignacio-chiazzo

LeetcodeProblems/Minimum_Window_Substring.js

@@ -0,0 +1,76 @@
+/*
+Minimum Window Substring
+
+https://leetcode.com/problems/minimum-window-substring/
+
+Given a string S and a string T, find the minimum window in S which will contain all the characters in T in complexity O(n).
+
+Example:
+
+Input: S = "ADOBECODEBANC", T = "ABC"
+Output: "BANC"
+Note:
+
+If there is no such window in S that covers all characters in T, return the empty string "".
+If there is such window, you are guaranteed that there will always be only one unique minimum window in S.
+*/
+
+
+var minWindow = function(s, t) {
+  if(t.length === 0 || s.length < t.length)
+    return "";
+  
+  var start = 0;
+  var end = 0;
+  var solutionStart, solutionEnd;
+  var hashT = getHash(t);
+  var currentHash = {};
+  var currentCount = 0;
+  while(end < s.length) {
+    const letter = s.charAt(end);
+    if(hashT[letter]) {
+      currentHash[letter] = (currentHash[letter]) ? currentHash[letter] + 1 : 1;
+      if(currentHash[letter] <= hashT[letter])
+        currentCount++;
+      if(currentCount === t.length) {
+        while(hashT[s[start]] === undefined || currentHash[s[start]] > hashT[s[start]]) {
+          if(currentHash[s[start]] !== undefined)
+            currentHash[s[start]] = currentHash[s[start]] - 1;
+          
+          start++;
+        }
+        if(solutionEnd === undefined || end - start < solutionEnd - solutionStart) {
+          solutionStart = start;
+          solutionEnd = end;
+        }
+
+        currentHash[s[start]] = currentHash[s[start]] - 1;
+        currentCount--;
+        start++;
+      }
+    }
+    end++;
+  }
+  
+  return s.slice(solutionStart, solutionEnd + 1);
+};    
+
+var getHash = function(t) {
+  var hash = {};
+  for(var i = 0; i < t.length; i++) {
+    const letter = t.charAt(i);
+    hash[letter] = (hash[letter]) ? hash[letter] + 1 : 1;
+  }
+  return hash;
+}
+
+var main = function() {
+  console.log(minWindow("ADOBECODEBANC", "ABC"));
+  console.log(minWindow("caaec", "cae"));
+  console.log(minWindow("bbacbb", "ab"));
+  console.log(minWindow("abba", "b"));
+  console.log(minWindow("abba", "a"));
+  console.log(minWindow("abba", ""));
+}
+
+module.exports.main