704. 二分查找 (二刷)

Author: w2xi

algorithms/binary-search.js

@@ -10,7 +10,9 @@ var search = function (nums, target) {
   let right = nums.length - 1;
 
   while (left <= right) {
-    const middle = Math.floor((left + right) / 2);
+    // const middle = Math.floor((left + right) / 2);
+    // 防止 left + right 过大导致溢出
+    const middle = left + ((right - left) >> 1)
 
     if (target < nums[middle]) {
       right = middle - 1;
@@ -24,21 +26,21 @@ var search = function (nums, target) {
   return -1;
 
   // 2. 递归
-  // const binarySearchRecursive = (array, left, right, target) => {
-  //   if (left <= right) {
-  //     const middle = Math.floor((left + right) / 2);
-
-  //     if (target < array[middle]) {
-  //       return binarySearchRecursive(array, left, middle - 1, target);
-  //     } else if (target > array[middle]) {
-  //       return binarySearchRecursive(array, middle + 1, right, target);
-  //     } else {
-  //       return middle;
-  //     }
-  //   } else {
-  //     return -1;
-  //   }
-  // };
-
   // return binarySearchRecursive(nums, 0, nums.length - 1, target);
 };
+
+function binarySearchRecursive(array, left, right, target) {
+  if (left <= right) {
+    const middle = left + ((right - left) >> 1)
+
+    if (target < array[middle]) {
+      return binarySearchRecursive(array, left, middle - 1, target);
+    } else if (target > array[middle]) {
+      return binarySearchRecursive(array, middle + 1, right, target);
+    } else {
+      return middle;
+    }
+  } else {
+    return -1;
+  }
+}