四种排序算法与二分查找

func BubbleSort(slice []int) []int {
	i, j, okay, count := 0, 0, true, len(slice)
	for i = 0; i < count-1; i++ { //最多需要进行count-1轮比较
		okay = true
		for j = 0; j < count-i-1; j++ { //每一轮比较的逻辑
			if slice[j] > slice[j+1] {
				slice[j], slice[j+1] = slice[j+1], slice[j]
				okay = false
			}
		}
		if okay { //当轮比较没有发生位置交换，说明已经排序完成，可提前退出循环
			break
		}
	}
	return slice
}

func InsertSort(slice []int) []int {
	var i, j int
	count := len(slice)
	for i = 1; i < count; i++ {
		for j = i; j > 0; j-- { //通过比较，找插入位置
			if slice[j-1] > slice[j] {
				slice[j-1], slice[j] = slice[j], slice[j-1]
			} else { //当前元素已找到插入位置，退出循环
				break
			}
		}
	}
	return slice
}

func SelectSort(slice []int) []int {
	var i, j, minKey int
	count := len(slice)
	for i = 0; i < count-1; i++ {
		minKey = i
		for j = i + 1; j < count; j++ { //找最小数位置
			if slice[minKey] > slice[j] {
				minKey = j
			}
		}
		if minKey != i {
			slice[minKey], slice[i] = slice[i], slice[minKey]
		}
	}
	return slice
}

func QuickSort(slice []int, start, end int) {
	if start >= end {
		return
	}
	i, j := start, end
	val := slice[(i+j)/2]
	for i <= j {
		for i <= end && slice[i] < val {
			i++
		}
		for j >= start && slice[j] > val {
			j--
		}
		if i <= j {
			slice[i], slice[j] = slice[j], slice[i]
			i++
			j--
		}
	}

	if start < j {
		QuickSort(slice, start, j)
	}
	if end > i {
		QuickSort(slice, i, end)
	}
}

func BinarySearch(slice []int, head, tail, value int) int {
	if head > tail {
		return -1
	}
	middle := (head + tail) / 2
	if slice[middle] == value {
		return middle
	} else if slice[middle] < value {
		return BinarySearch(slice, middle+1, tail, value)
	} else {
		return BinarySearch(slice, head, middle-1, value)
	}
}