added solution to Leetcode problem 771.Jewels and Stones

leetcode/771.c

@@ -0,0 +1,19 @@
+// for strlen( )
+#include<string.h>
+
+int numJewelsInStones(char * j, char * s){
+	// as strlen is O(n), store it once rather than using it in for loop
+    int cnt[500],lens=strlen(s),lenj=strlen(j),sol=0;
+    memset(cnt,0,sizeof(cnt));
+
+    // lookup to know which character occurs in j
+    for(int i=0;i<lenj;i++)
+        cnt[j[i]]++;
+
+    // count the characters in s
+    for(int i=0;i<lens;i++)
+        sol+=cnt[s[i]];
+
+    return sol;
+}
+