Add 76 in c language

Author: julienChemillier

c/76-Minimum-Window-Substring.c

@@ -0,0 +1,51 @@
+/*
+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 "".
+Space: O(1)
+Time: O(n+m) where n is the length of s and m the length of t
+*/
+
+char * minWindow(char * s, char * t){
+    int alpha[59] = {0};
+    int need = 0;
+    for (int i=0; t[i]!='\0'; i++) { // Initialise the alphabet
+        if (alpha[t[i]-'A']==0)
+            need++;
+        alpha[t[i]-'A']--;
+    }
+    int maxLen = 100001;
+    int pos=0;
+    int i=0, j=0;
+    while (s[j]!='\0') {
+        alpha[s[j]-'A']++;
+        if (alpha[s[j]-'A']==0) {
+            need--;
+            if (need==0) {
+                while (alpha[s[i]-'A']>0) {
+                    alpha[s[i]-'A']--;
+                    i++;
+                }
+                if ((j-i+1)<maxLen) {
+                    pos = i;
+                    maxLen = j-i+1;
+                }
+                alpha[s[i]-'A']--;
+                need++;
+                i++;
+            }
+        }
+        j++;
+    }
+    
+    if (maxLen==100001) { // No substring found
+        char* ans = malloc(sizeof(char));
+        ans[0] = '\0';
+        return ans;
+    } else {
+        char* ans = malloc(sizeof(char)*(maxLen+1));
+        for (int i=0; i<maxLen; i++)
+            ans[i] = s[i+pos];
+        ans[maxLen] = '\0';
+        return ans;
+    }
+}