D Xiaoyang buy fruit

 

Links: https://ac.nowcoder.com/acm/contest/949/D
Source: Cattle-off network

Title Description

Fruit store has $\mathrm{the\; n-\; the\; n-fruit\; in\; a\; row.\; The\; manager\; can\; only\; ask\; the\; customer\; to\; buy\; a\; contiguous\; fruit.\; Xiaoyang\; for\; each\; fruit\; has\; a\; likeability\; A\; i\; ai,\; the\; final\; degree\; of\; satisfaction\; as\; he\; likes\; to\; buy\; fruit\; and.\; And\; if\; positive\; (no\; matter\; how\; positive,\; as\; long\; as\; greater\; than\; 0\; 0\; can\; be),\; he\text{'}ll\; be\; happy.}$

Xiaoyang want to know to buy the maximum number of fruit under the conditions of his satisfaction.

$\mathrm{Can\; you\; help\; him?}$

Enter a description:

The first input line of a positive integer n, the total number of fruits. 

The second line of the input n integers ${\mathrm{A\; I\; AI,\; represents\; a\; small\; extent\; like\; for\; each\; of\; the\; male\; fruit.}}^{}$

Output Description:

A row of integer results. (If one can not buy fruit, please output 0)

Example 1

Entry

5
0 0 -7 -6 1

Export

1 

ideas: for each prefix and saved and the position of a structure. And descending order according to the prefix, the prefix, and according to the position equal descending rows. Traversing again. Records have traversed 
a minimum position minx, if the current position of the point of traversing a [i] .pos greater than the minimum front position, can update answer (a [i] .pos-minx ), and since the prefix is larger than it, It must be a 
positive number.  

However, to note is that we must add a zero, and the prefix 0, 0 position, if the test sample is only a 1-point, there is no point of comparison, so to add a zero. 
In fact, the prefix and equal by location descending row is very important because guarantees a minimum position in front of the prefix and must be smaller than it. Prefix and will not appear equal, resulting in an updated 
answer wrong. 
Code:

#include<iostream>
#include<algorithm>
#include<cstdio>
#include<cstring>
#define inf 0x3f3f3f3f
using namespace std;
typedef long long ll;
const int maxn=2e6+100;
struct node{
    int num,pos;
}e[maxn];
bool cmp(node a,node b)//排序 
{
    if(a.num==b.num)
        return a.pos>b.pos;
    return a.num<b.num;
}
int main()
{
    int n,x;
    scanf("%d",&n);
    for(int i=1;i<=n;i++)
    {
        scanf("%d",&x);
        e[i].num=x+e[i-1].num;//前缀和 
        e[i].pos=i;//位置 
    }
    n++;
    sort(e+1,e+n+1,cmp);
    int minx=n;
    int ans=0;
    for(int i=1;i<=n;i++)
    {
        minx=min(minx,e[i].pos);
        if(e[i].pos>minx)
            ans=max(ans,e[i].pos-minx); 
    }
    printf("%d\n",ans);
    return 0;
}