1、704

（1）题目描述

（2）代码实现

package com.hh.practice.leetcode.array.demo_02;

public class BinarySearch_704 {

    public int search(int[] nums, int target) {
        int i= 0,j = nums.length -1;
        while (i <= j){
            int mid = (i+j) >>> 1;
            if (target < nums[mid]){
               j = mid - 1;
            } else if (nums[mid] < target) {
                i = mid + 1;
            }else {
                return mid;
            }
        }
        return -1;
    }
    //方式一
//    public int search(int[] nums, int target) {
//        for(int i = 0; i < nums.length; i++){
//            if(target == nums[i]){
//               return i;
//            }
//        }
//        return -1;
//    }
}

2、35

（1）题目描述

（2）代码实现

package com.hh.practice.leetcode.array.demo_02;

public class BinarySearch_35 {
    //方式二
    public static int searchInsert(int[] arr, int key) {
        int i = 0;
        int j = arr.length - 1;
        while (i <= j) {
            int mid = (i + j) >>> 1;
            if (key <= arr[mid]) {
                j = mid - 1;
            } else{
                i = mid + 1;
            }
        }
        return i;
    }
    //方式一
//    public int searchInsert(int[] nums, int target) {
//        int low = 0;
//        int high = nums.length - 1;
//
//        while (low <= high) {
//            int mid = (low + high) >>> 1;
//            int midVal = nums[mid];
//
//            if (midVal < target)
//                low = mid + 1;
//            else if (midVal > target)
//                high = mid - 1;
//            else
//                return mid; // target found
//        }
//        //没找到就返回插入点，
//        return low;  // target not found.
//    }
}

3、34

（1）题目描述‘

（2）代码实现

package com.hh.practice.leetcode.array.demo_02;

public class BinarySearch_34 {

    public int[] searchRange(int[] nums, int target) {
         int[] arr = new int[2];
         arr[0] = binaryLeft(nums,target);
         if (arr[0] == -1){
             arr[1] = -1;
         } else {
             arr[1] = binaryRight(nums, target);
         }
         return arr;
    }

    /*
         返回最靠左的元素索引
      */
    public int binaryLeft(int[] arr, int key) {
        int i = 0;
        int j = arr.length - 1;
        int candidate = -1;
        while (i <= j) {
            int mid = (i + j) >>> 1;
            if (key < arr[mid]) {
                j = mid - 1;
            } else if (key > arr[mid]) {
                i = mid + 1;
            } else {
                candidate = mid;
                j = mid -1;
            }
        }
        return candidate;
    }
    /*
    返回最靠右的元素索引
 */
    public int binaryRight(int[] arr, int key) {
        int i = 0;
        int j = arr.length - 1;
        int candidate = -1;
        while (i <= j) {
            int mid = (i + j) >>> 1;
            if (key < arr[mid]) {
                j = mid - 1;
            } else if (key > arr[mid]) {
                i = mid + 1;
            } else {
                candidate = mid;
                i = mid +1;
            }
        }
        return candidate;
    }
}

 

 

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