add curly braces and comments to advoid confusion

Author: MengyiG

problems/0704.二分查找.md

@@ -174,13 +174,17 @@ class Solution {
         int left = 0, right = nums.length - 1;
         while (left <= right) {
             int mid = left + ((right - left) >> 1);
-            if (nums[mid] == target)
+            if (nums[mid] == target) {
                 return mid;
-            else if (nums[mid] < target)
+            }
+            else if (nums[mid] < target) {
                 left = mid + 1;
-            else if (nums[mid] > target)
+            }
+            else { // nums[mid] > target
                 right = mid - 1;
+            }
         }
+        // 未找到目标值
         return -1;
     }
 }
@@ -194,13 +198,17 @@ class Solution {
         int left = 0, right = nums.length;
         while (left < right) {
             int mid = left + ((right - left) >> 1);
-            if (nums[mid] == target)
+            if (nums[mid] == target) {
                 return mid;
-            else if (nums[mid] < target)
+            }
+            else if (nums[mid] < target) {
                 left = mid + 1;
-            else if (nums[mid] > target)
+            }
+            else { // nums[mid] > target
                 right = mid;
+            }
         }
+        // 未找到目标值
         return -1;
     }
 }