Minimum Window Substring solution

Author: PDKhan

minimum-window-substring/PDKhan.cpp

@@ -0,0 +1,44 @@
+class Solution {
+    public:
+        string minWindow(string s, string t) {
+            unordered_map<char, int> t_map;
+            unordered_map<char, int> window;
+            int need = 0, match = 0;
+            int min_len = INT_MAX;
+            int min_low = 0;
+            int l = 0;
+    
+            for(char ch : t){
+                if(t_map[ch] == 0)
+                    need++;
+    
+                t_map[ch]++;
+            }
+    
+            for(int h = 0; h < s.length(); h++){
+                window[s[h]]++;
+    
+                if(window[s[h]] == t_map[s[h]])
+                    match++;
+                
+                while(need == match){
+                    if(h - l + 1 < min_len){
+                        min_len = h - l + 1;
+                        min_low = l;
+                    }
+    
+                    window[s[l]]--;
+    
+                    if(window[s[l]] < t_map[s[l]])
+                        match--;
+                    
+                    l++;
+                }            
+            }
+    
+            if(min_len == INT_MAX)
+                return "";
+            
+            return s.substr(min_low, min_len);
+        }
+    };