HDU 5183 Negative and Positive (NP)

#include<iostream>
#include<cstdio>
#include<cstring>
#include<cmath>
#include<algorithm>
#include<set>
using namespace std;
#define ll long long
#define pb push_back
#define mem(a,b) memset(a,b,sizeof(a)) 

inline int read(){  
   int s=0,w=1;  
   char ch=getchar();  
   while(ch<‘0‘||ch>‘9‘){if(ch==‘-‘)w=-1;ch=getchar();}  
   while(ch>=‘0‘&&ch<=‘9‘) s=s*10+ch-‘0‘,ch=getchar();  
   return s*w;  
} 

const int N=1e6+5;
ll a[N];
ll sum[N]={0};
set<ll>s;
int main()
{
    /*ios::sync_with_stdio(false);
    cin.tie(0);*/
    int t,cnt=0;
    scanf("%d",&t);
    while(t--)
    {
        cnt++;
        int n,k;
        scanf("%d %d",&n,&k);
        getchar();
        for(int i=1;i<=n;i++)a[i]=read();
        for(int i=1;i<=n;i++)sum[i]=sum[i-1]+(i%2?a[i]:-a[i]);
        /*for(int i=1;i<=n;i++)cout<<a[i]<<‘ ‘;
        cout<<endl;*/
        bool f=false;
        for(int i=n;i>=1;i--)
        {
            s.insert(sum[i]);
            if(i&1)
            {
                if(s.find(sum[i-1]+k)!=s.end())
                {
                    f=true;
                    break;
                }
            }
            else
            {
                if(s.find(sum[i-1]-k)!=s.end())
                {
                    f=true;
                    break;
                }
            }
        }
        printf("Case #%d: ",cnt);
        if(f)puts("Yes.");
        else puts("No.");
        s.clear();
    }
    return 0;
}