dp 最大子段和

注意：在實際問題中可能題目要求至少選一個，可能可以一個都不選

只返回最大子段和

#include<iostream>
#include<algorithm>
using namespace std;
const int maxn = 2e5 + 10;
const int inf = 0x7fffffff;

int n;
int a[maxn];
int maxsum(){
	int cur = 0,res = -inf;
	for(int i = 0; i < n; i++){
		cur = max(cur + a[i], a[i]);
		if(cur > res)  res = cur;
	}
	return res;
}
int main()
{
	cin>>n;
	for(int i = 0; i < n; i++){
		cin>>a[i];
	}
	cout<<maxsum()<<endl;  //如果返回值小於0，可以置零表示一個都不選
	return 0;
}

返回結果並返回左右端點位置

#include<iostream>
#include<algorithm>
using namespace std;
const int maxn = 2e5 + 10;
const int inf = 0x7fffffff;
int n;
int a[maxn];
int maxsum(int &start,int &ed){
	int cur = 0, res = -inf;
	int temp = 1;
	for(int i = 1; i <= n; i++){
		cur += a[i];
		if(cur > res){
			res = cur;
			start = temp;
			ed = i;
		}
		if(cur < 0){
			cur = 0;
			temp = i + 1;
		}
	}
	return res;
}
int main()
{
	cin>>n;
	for(int i = 1; i <= n; i++){
		cin>>a[i];
	}
	int s,t;
	cout<<maxsum(s,t)<<endl;  //if返回值小於0，可以一個都不選，則置爲0
	cout<<s<<' '<<t<<endl;
	return 0;
}