awesome-golang-algorithm/lib/Search.go at main · Golang-Solutions/awesome-golang-algorithm · GitHub

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package Solution

//	普通搜索
func BinarySearch(nums []int, target int) int {
	left, right := 0, len(nums)-1

	for left < right {
		mid := left + (right-left)/2
		if nums[mid] == target {
			return mid
		} else if nums[mid] < target {
			left = mid + 1
		} else if nums[mid] > target {
			right = mid - 1
		}
	}

	return -1
}

//	左边界
func BinarySearchLeftBound(nums []int, target int) int {
	left, right := 0, len(nums)-1

	for left <= right {
		mid := left + (right-left)/2
		if nums[mid] == target {
			right = mid - 1
		} else if nums[mid] < target {
			left = mid + 1
		} else if nums[mid] > target {
			right = mid - 1
		}
	}
	if nums[left] != target || left > len(nums) {
		return -1
	}
	return left
}

//	右边界
func BinarySearchRightBound(nums []int, target int) int {
	left, right := 0, len(nums)-1

	for left <= right {
		mid := left + (right-left)/2
		if nums[mid] == target {
			left = mid + 1
		} else if nums[mid] < target {
			left = mid + 1
		} else if nums[mid] > target {
			right = mid - 1
		}
	}
	if right < 0 || nums[right] != target {
		return -1
	}
	return right
}