package binary_search;
/**
 * 题目： 34. 在排序数组中查找元素的第一个和最后一个位置 (searchRange)
 * 描述：给你一个按照非递减顺序排列的整数数组 nums，和一个目标值 target。请你找出给定目标值在数组中的开始位置和结束位置。
 * 如果数组中不存在目标值 target，返回 [-1, -1]。
 * 你必须设计并实现时间复杂度为 O(log n) 的算法解决此问题。

 * 示例 1：
 输入：nums = [5,7,7,8,8,10], target = 8
 输出：[3,4]

 * 链接：https://leetcode.cn/problems/find-first-and-last-position-of-element-in-sorted-array/
 */
public class SearchRange {
    //极端情况下不是O(log n)
    public int[] searchRange(int[] nums, int target) {
        int left=0,right=nums.length-1;
        int tpleft=-1,tpright=-1;
        while (left<=right){
            int mid=(left+right)/2;
            if(target==nums[mid]){
                tpleft=mid-1;
                tpright=mid+1;
                while (tpleft>=left) {
                    if (target == nums[tpleft])
                        tpleft--;
                    else
                        break;
                }
                tpleft++;
                while (tpright<=right) {
                    if (target == nums[tpright])
                        tpright++;
                    else
                        break;
                }
                tpright--;
                break;
            }
            else if(target>nums[mid])
                left=mid+1;
            else
                right=mid-1;
        }
        return new int[]{tpleft,tpright};
    }

    private int findLeft(int[] nums, int target) {
        int left = 0, right = nums.length - 1;
        int index = -1;
        while (left <= right) {
            int mid = left + (right - left) / 2;
            if (nums[mid] >= target) {
                right = mid - 1;
            } else {
                left = mid + 1;
            }
            if (nums[mid] == target) {
                index = mid;
            }
        }
        return index;
    }

    // 找到目标值的最后一次出现位置
    private int findRight(int[] nums, int target) {
        int left = 0, right = nums.length - 1;
        int index = -1;
        while (left <= right) {
            int mid = left + (right - left) / 2;
            if (nums[mid] <= target) {
                left = mid + 1;
            } else {
                right = mid - 1;
            }
            if (nums[mid] == target) {
                index = mid;
            }
        }
        return index;
    }

    public int[] searchRange1(int[] nums, int target) {
        int leftIndex = findLeft(nums, target);
        int rightIndex = findRight(nums, target);
        return new int[]{leftIndex, rightIndex};
    }
}