差分数组

 

 差分数组的适用场景是：频繁对原始数组的某个区间的元素进⾏增减。

//第一步：构建差分数组
func Diff(nums []int)[]int{
	m:=len(nums)
	if m==0{
		return []int{}
	}
	diff:=make([]int,m)
	diff[0]=nums[0]
	for i:=1;i<m;i++{
		diff[i]=nums[i]-nums[i-1]
	}
	return diff
}

//第二步：给闭区间[i,j]增加val
func Increment(diff []int,i ,j, val int){
	diff[i]+=val
	if j+1<len(diff){
		diff[j+1]-=val
	}
}

//第三步：返回结果数组
func Result(diff []int)[]int{
	if len(diff)==0{
		return []int{}
	}
	res:=make([]int,len(diff))
	res[0]=diff[0]
	for i:=1;i<len(diff);i++{
		res[i]=res[i-1]+diff[i]
	}
	return res
}