P5019 分治做法

#include<bits/stdc++.h>
using namespace std;
int n,a[100010],ans;
void floor(int x,int y){
	int minn=0x7ffffff,p,i;
	if(x>y) return;
	for(i=x;i<=y;i++){
		p=a[i]<minn? i:p;
		minn=a[i]<minn? a[i]:minn;
	}
	for(i=x;i<=y;i++){
		a[i]-=minn;
	}
	ans+=minn;
	floor(x,p-1);
	floor(p+1,y);
}
int main(){
	cin>>n;
	for(int i=1;i<=n;i++){
		cin>>a[i];
	}
	floor(1,n);
	cout<<ans;
}