add c solution to statement

string/statement.md

@@ -59,7 +59,24 @@ i
 ## C
 
 ```
-
+#include <stdio.h>
+#include <string.h>
+
+char buf[200];
+
+int main(int argc, char const *argv[])
+{
+  int T;
+  scanf("%d", &T);
+  while(T--){
+    int n, k;
+    scanf("%s %d", buf, &k);
+    n = strlen(buf);
+    if(k > n)printf("*\n");
+    else printf("%c\n", buf[k-1]);
+  }
+  return 0;
+}
 ```
 
 ## Java