fixed binary search (#64)

Author: realDuYuanChao

searches/binary_search.c

@@ -11,7 +11,7 @@ int search(const int *arr, int len, int key) {
     int low = 0;
     int high = len - 1;
     while (low <= high) {
-        int mid = (low + high) >> 1;
+        int mid = low + (high - low) / 2;
         if (key == arr[mid]) {
             return mid;
         } else if (key > arr[mid]) {

searches/binary_search_recursion.c

@@ -12,13 +12,13 @@ int search(const int *arr, int key, int low, int high) {
     if (low > high) {
         return -1;
     }
-    int mid = (low + high) / 2;
+    int mid = low + (high - low) / 2;
     if (key == arr[mid]) {
         return mid;
     } else if (key > arr[mid]) {
         return search(arr, key, mid + 1, high);
     } else {
-        return search(arr, key, 0, mid - 1);
+        return search(arr, key, low, mid - 1);
     }
 }