Submission #2099334

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Source Code Expand

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#define pb push_back
#define fs first
#define sc second
#define all(x) (x).begin(), (x).end()
#define sz(x) (int)(x).size()
using namespace std;
using namespace __gnu_pbds;

typedef long long ll;
typedef vector<int> vi;
typedef vector<ll> vll;
typedef vector<double> vd;
typedef pair<int, int> pii;
typedef pair<ll, int> plli;
typedef vector<pii> vpii;
typedef tree<pii, null_type, less<pii>, rb_tree_tag,
    tree_order_statistics_node_update> ost;

const int N=4010;
const ll P=1e9+7;
const ll PH=(P+1)/2;
int bn[2*N][2*N];
ll t[2*N];

int main() {
    int i, j, n, a, b, ans=0;
    for(i=0; i<2*N; i++) bn[i][0]=1;
    for(i=1; i<2*N; i++) for(j=1; j<=i; j++) {
        bn[i][j]=bn[i-1][j]+bn[i-1][j-1];
        if(bn[i][j]>=P) bn[i][j]-=P;
    }
    scanf("%d", &n);
    for(i=0; i<n; i++) {
        scanf("%d%d", &a, &b);
        ans=(ans+P-bn[2*a+2*b][2*b])%P;
        for(j=0; j<=a+b; j++)
            t[N-a+j]+=bn[a+b][j];
    }
    for(i=-N+1; i<N; i++) t[N+i]%=P;
    for(i=-N+1; i<N; i++)
        ans=(ans+t[i+N]*t[-i+N])%P;
    printf("%lld\n",ans*PH%P);
    return 0;
}

Submission Info

Compile Error

./Main.cpp: In function ‘int main()’:
./Main.cpp:34:20: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d", &n);
                    ^
./Main.cpp:36:30: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d%d", &a, &b);
                              ^

Judge Result