hello-algo/codes/go/chapter_searching/binary_search_edge.go
2023-08-24 17:48:35 +08:00

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// File: binary_search_edge.go
// Created Time: 2023-08-23
// Author: Reanon (793584285@qq.com)
package chapter_searching
/* 二分查找最左一个 target */
func binarySearchLeftEdge(nums []int, target int) int {
// 等价于查找 target 的插入点
i := binarySearchInsertion(nums, target)
// 未找到 target ,返回 -1
if i == len(nums) || nums[i] != target {
return -1
}
// 找到 target ,返回索引 i
return i
}
/* 二分查找最右一个 target */
func binarySearchRightEdge(nums []int, target int) int {
// 转化为查找最左一个 target + 1
i := binarySearchInsertion(nums, target+1)
// j 指向最右一个 target i 指向首个大于 target 的元素
j := i - 1
// 未找到 target ,返回 -1
if j == -1 || nums[j] != target {
return -1
}
// 找到 target ,返回索引 j
return j
}