link: http://codeforces.com/contest/330/problem/B
I think the problem is hard at first. However, when you think deep in it you will find it is so easy.
1 /* 2 ID: zypz4571 3 LANG: C++ 4 TASK: 192b.cpp 5 */ 6 7 #include <iostream> 8 #include <cstdio> 9 #include <cstdlib> 10 #include <cstring> 11 #include <cmath> 12 #include <cctype> 13 #include <algorithm> 14 #include <queue> 15 #include <deque> 16 #include <queue> 17 #include <list> 18 #include <map> 19 #include <set> 20 #include <vector> 21 #include <utility> 22 #include <functional> 23 #include <fstream> 24 #include <iomanip> 25 #include <sstream> 26 #include <numeric> 27 #include <cassert> 28 #include <ctime> 29 30 #define INF 0x3f3f3f3f 31 #define REP(i, n) for(int i=0;i<int(n);++i) 32 #define FOR(i, a, b) for(int i=int(a);i<int(b);++i) 33 #define DWN(i, b, a) for(int i=int(b-1);i>=int(a);--i) 34 #define REP_1(i, n) for(int i=1;i<=int(n);++i) 35 #define mid int m=(l+r)/2 36 using namespace std; 37 int main ( int argc, char *argv[] ) 38 { 39 #ifndef ONLINE_JUDGE 40 freopen("in.txt", "r", stdin); 41 #endif 42 int n, m; cin >> n >> m; 43 multiset<int> rp; 44 int a, b; 45 REP (i, m) { 46 cin >> a >> b; 47 rp.insert(a); rp.insert(b); 48 } 49 int tmp; 50 FOR(i, 1, n+1) { 51 if (rp.count(i) == 0) { 52 tmp = i; break; 53 } 54 } 55 cout <<n-1<<endl; 56 FOR (i, 1, n+1) { 57 if (i != tmp) { 58 cout << min(tmp, i) <<' '<<max(tmp,i)<<endl; 59 } 60 } 61 return EXIT_SUCCESS; 62 } /* ---------- end of function main ---------- */
It seems that I can not use STL very skillfully.
