动态规划做法

#include <bits/stdc++.h>
using namespace std;
using ll = long long;

ll a[1005][1005];

int main()
{
    int n, m;
    cin >> n >> m;
    while (m--) {
        int x, y;
        cin >> x >> y;
        a[x][y] = -1;
    }
    a[1][1] = 1;
    for (int i = 1; i <= n; i++) {
        for (int j = 1; j <= n; j++) {
            if (i == 1 && j == 1) continue;
            if (a[i][j] == -1) {
                a[i][j] = 0;
                continue;
            }
            a[i][j] = (a[i - 1][j] + a[i][j - 1]) % 100003;
        }
    }
    cout << a[n][n] << endl;
    return 0;
}