Add 76 in c language

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;
+ }
+}