LeetCode34. 在排序数组中查找元素的第一个和最后一个位置

LeetCode34. 在排序数组中查找元素的第一个和最后一个位置

1. 题目跳转
2. 二分边界问题参考
3. JAVA代码:

class Solution {
    public int[] searchRange(int[] nums, int target) {
        if (nums.length == 0) return new int[]{-1, -1};
        int[] res = new int[2];
        res[0] = binarySearchFirst(nums, target, 0, nums.length);
        res[1] = res[0] == -1 ? -1 : binarySearchSecond(nums, target, 0, nums.length);
        return res;
    }

    //查找左边界
    private int binarySearchFirst(int[] nums, int target, int left, int right) {
        while (left < right) {
            int mid = left + ((right - left) >> 1);
            if (nums[mid] >= target) {
                right = mid;
            } else if (nums[mid] < target) {
                left = mid + 1;
            }
        }
        if (left == nums.length) return -1;
        return nums[left] == target ? left : -1;
    }

    //查找右边界
    private int binarySearchSecond(int[] nums, int target, int left, int right) {
        while (left < right) {
            int mid = left + ((right - left) >> 1);
            if (nums[mid] > target) {
                right = mid;
            } else if (nums[mid] <= target) {
                left = mid + 1;
            }
        }
        if (left == 0) return -1;
        return nums[left - 1] == target ? (left - 1) : -1;
    }
}