【LeetCode】 59 在排序数组中查找元素的第一个和最后一个位置

题目：

解题思路：

二分法

https://leetcode-cn.com/problems/find-first-and-last-position-of-element-in-sorted-array/solution/zai-pai-xu-shu-zu-zhong-cha-zhao-yuan-su-de-di-yi-/

代码：

package com.janeroad;

/**
 * Created on 2020/7/16.
 *
 * [@author](https://my.oschina.net/arthor) LJN
 */
public class Test22 {
    // returns leftmost (or rightmost) index at which `target` should be
    // inserted in sorted array `nums` via binary search.
    private int extremeInsertionIndex(int[] nums, int target, boolean left) {
        int lo = 0;
        int hi = nums.length;

        while (lo < hi) {
            int mid = (lo + hi) / 2;
            if (nums[mid] > target || (left && target == nums[mid])) {
                hi = mid;
            }
            else {
                lo = mid+1;
            }
        }

        return lo;
    }

    public int[] searchRange(int[] nums, int target) {
        int[] targetRange = {-1, -1};

        int leftIdx = extremeInsertionIndex(nums, target, true);

        // assert that `leftIdx` is within the array bounds and that `target`
        // is actually in `nums`.
        if (leftIdx == nums.length || nums[leftIdx] != target) {
            return targetRange;
        }

        targetRange[0] = leftIdx;
        targetRange[1] = extremeInsertionIndex(nums, target, false)-1;

        return targetRange;
    }

    public static void main(String[] args) {
        Test22 test22=new Test22();
        int[] nums=new int[]{1,3,5,8,8,8,23};
        int[] ints = test22.searchRange(nums, 8);
        for (int i = 0; i < ints.length; i++) {
            System.out.println(ints[i]);
        }
    }

}

来源：oschina

链接：https://my.oschina.net/u/4248053/blog/4396863