modified completed 14425.c

zeta_C/completed/14425.c

@@ -4,13 +4,22 @@
 
 int STR_LEN = 501;
 
-int is_in(char *a, char (*S)[STR_LEN], int N) {
+int comp(const void *a, const void *b) {
+    return strcmp((char *) a, (char *) b);
+}
 
-    for (int i = 0; i < N; i++) {
-        int c = strcmp(a, S[i]);
-        if (c == 0) {
-            return 1;
-        }
+int is_in(char *a, char (*S)[STR_LEN], int N) {
+    // binary search
+    int low = 0, high = N - 1;
+    while (low <= high) {
+        int mid = (low + high) / 2;
+
+        int k = (int) strcmp(a, S[mid]);
+        if (k == 0) return 1;
+        else if (k < 0)
+            high = mid - 1;
+        else if (k > 0)
+            low = mid + 1;
     }
     return 0;
 }
@@ -31,6 +40,8 @@ int main() {
         scanf("%s", (check[i]));
     }
 
+    qsort(S, N, sizeof(char) * 501, comp);
+
     int count = 0;
     for (int i = 0; i < M; i++) {
         count += is_in((check[i]), S, N);