【PAT】甲级1007 - Maximum Subsequence Sum (最大子序列的和)

#include<queue>
#include<cmath>
#include<stack>
#include<cstdio>
#include<vector>
#include<cstring>
#include<iostream>
#include<algorithm>
using namespace std;
typedef long long LL;
#define INF 0x3f3f3f3f
#define CLR(a,b) memset(a,b,sizeof(a))
#define PI acos(-1.0)
int main()
{
    int n;
    int num[10000+5];
    bool isAllNotPositive = true;
    bool isHaveZero = false;
    cin >> n;
    for (int i = 1 ; i <= n ; i++)
    {
        scanf ("%d",&num[i]);
        if (num[i] > 0)
            isAllNotPositive = false;
        if (num[i] == 0)
            isHaveZero = true;
    }
    if (isAllNotPositive)       //如果都是非正数 
    {
        if (isHaveZero)     //先判断0 
        {
            for (int i = 1 ; i <= n ; i++)
            {
                if (num[i] == 0)
                {
                    printf ("0 %d %d\n",num[i],num[i]);
                    break;
                }
            }
        }
        else        //都是负数 
        {
            printf ("0 %d %d\n",num[1],num[n]);
        }
        return 0;
    }
    LL sum = 0;
    LL MaxSum = 0;
    int st,endd,temp_st = 1;
    for (int i = 1 ; i <= n ; i++)
    {
        sum += num[i];
        if (sum > MaxSum)
        {
            st = temp_st;
            endd = i;
            MaxSum = sum;
        }
        if (sum < 0)
        {
            temp_st = i+1;
            sum = 0;
        }
    }
    printf ("%lld %d %d\n",MaxSum,num[st],num[endd]);
    return 0;
}