【Hot100】LeetCode—34. 在排序数组中查找元素的第一个和最后一个位置

本文主要是介绍【Hot100】LeetCode—34. 在排序数组中查找元素的第一个和最后一个位置，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

1- 思路

二分 - 左侧二分 + 右侧二分

右区间二分 ——> 找首次出现的位置 ——>nums[mid] >= target
左区间二分 ——> 找最后一次出现的位置 ——> **nums**[mid] <= target

2- 实现

⭐34. 在排序数组中查找元素的第一个和最后一个位置——题解思路

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class Solution {public int[] searchRange(int[] nums, int target) {int[] res = new int[2];Arrays.fill(res,-1);if(nums.length == 0 || nums==null){return res;}int left = 0;int right = nums.length-1;while(left<right){int mid = (left+right)/2;if(nums[mid] >= target){right = mid;}else{left = mid+1;}}if(nums[left]==target){res[0] = left;}left = 0;right = nums.length-1;while(left<right){int mid = (left+right+1)/2;if(nums[mid] <= target){left = mid;}else{right = mid-1;}}if(nums[left]==target){res[1] = left;}return res;}
}

3- ACM 实现

public class findFirstAndLast {public static int[] finFAndL(int[] nums,int target){int[] res = new int[2];Arrays.fill(res,-1);int left = 0;int right = nums.length-1;while(left<right){int mid = (left+right)/2;if(nums[mid] >= target){right = mid;}else{left = mid+1;}}if(res[left]==target){res[0] = left;}left = 0;right = nums.length-1;while(left<right){int mid = (left+right+1)/2;if(nums[mid] <= target){left = mid;}else{right = mid-1;}}if(res[left]==target){res[1] = left;}return res;}public static void main(String[] args) {Scanner sc = new Scanner(System.in);String input = sc.nextLine();input = input.substring(1,input.length()-1);String[] parts = input.split(",");int[] nums = new int[parts.length];for(int i = 0 ; i < nums.length;i++){nums[i] = Integer.parseInt(parts[i]);}System.out.println("输入target");int target = sc.nextInt();int[] res = finFAndL(nums,target);System.out.println("结果是"+res[0]+" "+res[1]);}
}