Road Construction

包裝陷阱題

其實只要讓一個點在內心，其他所有點要連到其他點都只要兩步，而且保證最少road

//====================================================================||
// Name        : Road Construction.cpp                                              ||
// Date : 2013/7/20 下午10:13:31                                               ||
// Author : GCA                                                       ||
//                  6AE7EE02212D47DAD26C32C0FE829006                  ||
//====================================================================||
#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
#include <climits>
#include <vector>
#include <set>
#include <map>
#include <queue>
#include <cctype>
#include <utility>
using namespace std;
#ifdef ONLINE_JUDGE
#define ll "%lld"
#else
#define ll "%I64d"
#endif
typedef unsigned int uint;
typedef long long int Int;
#define Set(a,s) memset(a,s,sizeof(a))
#define Write(w) freopen(w,"w",stdout)
#define Read(r) freopen(r,"r",stdin)
#define Pln() printf("\n")
#define I_de(x,n)for(int i=0;i<n;i++)printf("%d ",x[i]);Pln()
#define De(x)printf(#x"%d\n",x)
#define For(i,x)for(int i=0;i<x;i++)
#define CON(x,y) x##y
#define Pmz(dp,nx,ny)for(int hty=0;hty<ny;hty++){for(int htx=0;htx<nx;htx++){\
    printf("%d ",dp[htx][hty]);}Pln();}
#define M 1004
#define PII pair<int,int>
#define PB push_back
#define oo INT_MAX
#define Set_oo 0x3f
#define Is_debug true
#define debug(...) if(Is_debug)printf("DEBUG: "),printf(__VA_ARGS__)
#define FOR(it,c) for(__typeof((c).begin()) it=(c).begin();it!=(c).end();it++)
#define eps 1e-6
bool xdy(double x,double y){return x>y+eps;}
bool xddy(double x,double y){return x>y-eps;}
bool xcy(double x,double y){return x<y-eps;}
bool xcdy(double x,double y){return x<y+eps;}
int min3(int x,int y,int z){
    int tmp=min(x,y);
    return min(tmp,z);
}
int max3(int x,int y,int z){
    int tmp=max(x,y);
    return max(tmp,z);
}
int n,m;
int mz[M][M];
int con[M][M];
bool canused[M];
int main() {
    ios_base::sync_with_stdio(0);
    while(~scanf("%d%d",&n,&m)){
        Set(con,0);
        Set(mz,0);
        for(int i=0;i<n;i++)canused[i]=1;
        while(m--){
            int x,y;
            scanf("%d%d",&x,&y);
            x--;y--;
            canused[x]=canused[y]=0;
        }
        int index;
        for(int i=0;i<n;i++){
            if(canused[i]){
                index=i;
            }
        }
        printf("%d\n",n-1);
        for(int i=0;i<n;i++){
            if(i==index)continue;
            printf("%d %d\n",i+1,index+1);
        }
    }


}