cppProgram/Grid_Paths.cpp at main · Tirthankarpal/cppProgram · GitHub

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#include "bits/stdc++.h"
//#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll MOD = 1e9+7;
int main(){
    ll n,m;
    cin>>n>>m;
    vector<vector<ll>> arr(n,vector<ll>(n,0));
    for(int s=0;s<m;s++){
        int i,j;
        cin>>i>>j;
        arr[i-1][j-1]=-1;
    }
    if(arr[0][0] == -1) {
        cout << 0 << endl;
        return 0;
    }
    arr[0][0] = 1;
    bool f=false;
    for(int i=0;i<n;i++){
        if(arr[i][0]==-1){
            f=true;
        }
        if(f)arr[i][0]=0;
        else arr[i][0]=1;
    }
    f=false;
    for(int i=0;i<n;i++){
        if(arr[0][i]==-1){
            f=true;
        }
        if(f)arr[0][i]=0;
        else arr[0][i]=1;
    }
    for(int i=1;i<n;i++){
        for(int j=1;j<n;j++){
            if(arr[i][j]==-1){
                arr[i][j] = 0;
                continue;
            }
            arr[i][j] = (arr[i][j] + arr[i-1][j]) % MOD;
            arr[i][j] = (arr[i][j] + arr[i][j-1]) % MOD;
        }
    }
    cout<<arr[n-1][n-1]<<endl;
}