Codeforces 330B Road Construction

题目链接：Codeforces 330B Road Construction

m < n / 2，所以必然有一个节点与所有边都相连(画出来的。。)，所以边数就是n - 1。

#include<iostream>#include <cstring>using namespace std;bool e[1001];int main(){    int n,m;    int x,y;    memset(e,0,sizeof(e));    cin >> n >> m;    int i;    for (i = 0; i < m; i++)    {        cin >> x >> y;        e[x] = e[y] = true;    }    for (i = 1; i <= n; i++)        if (!e[i])            break;    cout << n -1 << endl;    for (int j = 1; j <= n; j++)        if (i != j) cout << j << " " << i <<endl;}