【重点】【二分查找】34. 在排序数组中查找元素的第一个和最后一个位置-优快云博客

本文详细介绍了如何使用Java编写一个名为Solution的类，实现二分查找算法，包括findLeftBoundary和findRightBoundary方法，以找到目标值在给定数组中的左右边界。

法1：二分查找，最佳解法！！！

class Solution:
    def searchRange(self, nums: List[int], target: int) -> List[int]:
        start = self.find(nums, target)
        end = self.find(nums, target + 1) - 1

        return [start, end] if start <= end else [-1, -1]
    
    def find(self, nums, target):
        l, r = 0, len(nums)-1
        while l <= r:
            mid = (l + r) // 2
            if nums[mid] < target:
                l = mid + 1
            else:
                r = mid - 1
            
        return l

class Solution {
    public int[] searchRange(int[] nums, int target) {
        if (nums.length == 0) {
            return new int[]{-1, -1};
        }
        int n = nums.length;
        int left = findLeftBoundary(nums, target, 0, n - 1);
        int right = findRightBoundary(nums, target, 0, n - 1);
        if (left <= right) {
            return new int[]{left, right};
        }

        return new int[]{-1, -1};
    }

    public int findLeftBoundary(int[] nums, int target, int start, int end) {
        while (start <= end) {
            int mid = start + (end - start) / 2;
            if (nums[mid] >= target) {
                end = mid - 1;
            } else {
                start = mid + 1;
            }
        }

        return start;
    }


    public int findRightBoundary(int[] nums, int target, int start, int end) {
        while (start <= end) {
            int mid = start + (end - start) / 2;
            if (nums[mid] <= target) {
                start = mid + 1;
            } else {
                end = mid - 1;
            }
        }

        return end;
    }
}