拆点连边就好了,网络流水题……
/* Author : Speedcell Update : 2013-05-30 Version : soppYcell 2.2(a) */ #include <algorithm> #include <iostream> #include <fstream> #include <sstream> #include <iomanip> #include <map> #include <set> #include <list> #include <stack> #include <queue> #include <deque> #include <vector> #include <string> #include <bitset> #include <memory> #include <complex> #include <numeric> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <math.h> #include <time.h> #include <ctype.h> #include <locale.h> using namespace std; #pragma pack(4) #ifndef __CONSTANT__ #define __CONSTANT__ typedef long long LONG; const double pi = acos(-1.0); const int inf = 0x7f7f7f7f; const LONG INF = 0x7f7f7f7f7f7f7f7fll; const int go[8][2] = {{0,1},{0,-1},{1,0},{-1,0},{1,1},{1,-1},{-1,1},{-1,-1}}; #endif // __CONSTANT__ #ifndef __IO__ #define __IO__ inline bool RD(int & a) {return scanf("%d",&a)!=EOF;} inline bool RD(char & a) {return scanf("%c",&a)!=EOF;} inline bool RD(char * a) {return scanf("%s", a)!=EOF;} inline bool RD(double & a) {return scanf("%lf",&a)!=EOF;} inline bool RD(LONG & a) {return scanf("%I64d",&a)!=EOF;} template<class T1> inline bool IN(T1 & a) {return RD(a);} template<class T1,class T2> inline bool IN(T1 & a,T2 & b) {return RD(a)&&RD(b);} template<class T1,class T2,class T3> inline bool IN(T1 & a,T2 & b,T3 & c) {return RD(a)&&RD(b)&&RD(c);} template<class T1,class T2,class T3,class T4> inline bool IN(T1 & a,T2 & b,T3 & c,T4 & d) {return RD(a)&&RD(b)&&RD(c)&&RD(d);} template<class T1,class T2,class T3,class T4,class T5> inline bool IN(T1 & a,T2 & b,T3 & c,T4 & d,T5 & e) {return RD(a)&&RD(b)&&RD(c)&&RD(d)&&RD(e);} template<class T1,class T2,class T3,class T4,class T5,class T6> inline bool IN(T1 & a,T2 & b,T3 & c,T4 & d,T5 & e,T6 & f) {return RD(a)&&RD(b)&&RD(c)&&RD(d)&&RD(e)&&RD(f);} template<class T1,class T2,class T3,class T4,class T5,class T6,class T7> inline bool IN(T1 & a,T2 & b,T3 & c,T4 & d,T5 & e,T6 & f,T7 & g) {return RD(a)&&RD(b)&&RD(c)&&RD(d)&&RD(e)&&RD(f)&&RD(g);} inline void PT(int a) {printf("%d",a);} inline void PT(char a) {printf("%c",a);} inline void PT(char * a) {printf("%s",a);} inline void PT(double a) {printf("%f",a);} inline void PT(LONG a) {printf("%I64d",a);} inline void PT(const char a[]) {printf("%s",a);} template<class T1> inline void OT(T1 a) {PT(a);} template<class T1,class T2> inline void OT(T1 a,T2 b) {PT(a),PT(' '),PT(b);} template<class T1,class T2,class T3> inline void OT(T1 a,T2 b,T3 c) {PT(a),PT(' '),PT(b),PT(' '),PT(c);} template<class T1,class T2,class T3,class T4> inline void OT(T1 a,T2 b,T3 c,T4 d) {PT(a),PT(' '),PT(b),PT(' '),PT(c),PT(' '),PT(d);} template<class T1,class T2,class T3,class T4,class T5> inline void OT(T1 a,T2 b,T3 c,T4 d,T5 e) {PT(a),PT(' '),PT(b),PT(' '),PT(c),PT(' '),PT(d),PT(' '),PT(e);} template<class T1,class T2,class T3,class T4,class T5,class T6> inline void OT(T1 a,T2 b,T3 c,T4 d,T5 e,T6 f) {PT(a),PT(' '),PT(b),PT(' '),PT(c),PT(' '),PT(d),PT(' '),PT(e),PT(' '),PT(f);} template<class T1,class T2,class T3,class T4,class T5,class T6,class T7> inline void OT(T1 a,T2 b,T3 c,T4 d,T5 e,T6 f,T7 g) {PT(a),PT(' '),PT(b),PT(' '),PT(c),PT(' '),PT(d),PT(' '),PT(e),PT(' '),PT(f),PT(' '),PT(g);} template<class T1> inline void OL(T1 a) {PT(a),PT('\n');} template<class T1,class T2> inline void OL(T1 a,T2 b) {PT(a),PT(' '),PT(b),PT('\n');} template<class T1,class T2,class T3> inline void OL(T1 a,T2 b,T3 c) {PT(a),PT(' '),PT(b),PT(' '),PT(c),PT('\n');} template<class T1,class T2,class T3,class T4> inline void OL(T1 a,T2 b,T3 c,T4 d) {PT(a),PT(' '),PT(b),PT(' '),PT(c),PT(' '),PT(d),PT('\n');} template<class T1,class T2,class T3,class T4,class T5> inline void OL(T1 a,T2 b,T3 c,T4 d,T5 e) {PT(a),PT(' '),PT(b),PT(' '),PT(c),PT(' '),PT(d),PT(' '),PT(e),PT('\n');} template<class T1,class T2,class T3,class T4,class T5,class T6> inline void OL(T1 a,T2 b,T3 c,T4 d,T5 e,T6 f) {PT(a),PT(' '),PT(b),PT(' '),PT(c),PT(' '),PT(d),PT(' '),PT(e),PT(' '),PT(f),PT('\n');} template<class T1,class T2,class T3,class T4,class T5,class T6,class T7> inline void OL(T1 a,T2 b,T3 c,T4 d,T5 e,T6 f,T7 g) {PT(a),PT(' '),PT(b),PT(' '),PT(c),PT(' '),PT(d),PT(' '),PT(e),PT(' '),PT(f),PT(' '),PT(g),PT('\n');} #endif // __IO__ #ifndef __MACRO__ #define __MACRO__ #define ML(times) int tcase; IN(tcase); FOR(times,1,tcase) #define FOR(i,a,b) for(int i=int(a),_##i=int(b);i<=_##i;i++) #define DWN(i,b,a) for(int i=int(b),_##i=int(a);_##i<=i;i--) #define ECH(i,u,pre,next) for(int i=int(pre[u]);i!=-1;i=int(next[i])) #define MEM(a,v) memset(a,v,sizeof(a)) #define CLR(a,v) FOR(_i##a,0,sizeof(a)/sizeof(a[0])-1) a[_i##a]=v #define LOOP(a,n) \ FOR(_i##a,0,(n)-1) \ OT(a[_i##a]),OT(_i##a!=__i##a?' ':'\n') #define LOOP2(a,n,m) \ FOR(_i##a,0,(n)-1) FOR(_j##a,0,(m)-1) \ OT(a[_i##a][_j##a]),OT(_j##a!=__j##a?' ':'\n') #define LOOPG(G,n,pre,next) \ FOR(_i##a,0,(n)-1) ECH(_j##a,_i##a,pre,next) \ OL(_i##a,G[_j##a].v,G[_j##a].w) #endif // __MACRO__ #ifndef __BIT__ #define __BIT__ template<class T> inline T lb(T i) {return i&-i;} template<class T> inline T lc(T i) {return i<<1;} template<class T> inline T rc(T i) {return i<<1|1;} template<class T> inline T at(T a,int i) {return a& (T(1)<<i);} template<class T> inline T nt(T a,int i) {return a^ (T(1)<<i);} template<class T> inline T s1(T a,int i) {return a| (T(1)<<i);} template<class T> inline T s0(T a,int i) {return a&~(T(1)<<i);} #endif // __BIT__ #ifndef __DOUBLE__ #define __DOUBLE__ const double eps = 1e-8; inline int cmp(double a,double b=0) {return fabs(a-b)<eps?0:((a-b)>eps?+1:-1);} inline double fmax(double a,double b) {return cmp(a,b)>0?a:b;} inline double fmin(double a,double b) {return cmp(a,b)<0?a:b;} #endif // __DOUBLE__ const int MAXV = 120*2; const int MAXE = MAXV*MAXV*2; struct node { int v,w; }G[MAXE]; int _index,pre[MAXV],next[MAXE]; void clear(void) { _index=0; MEM(pre,-1); } void add(int u,int v,int w) { G[_index].v=v; G[_index].w=w; next[_index]=pre[u]; pre[u]=_index++; G[_index].v=u; G[_index].w=0; next[_index]=pre[v]; pre[v]=_index++; } int dis[MAXV],gap[MAXV],prev[MAXV],curr[MAXV],head[MAXV]; int SAP(int src,int des,int n) { int u=src,sum=0; memcpy(head,pre,MAXV-1); MEM(dis,0); MEM(gap,0); gap[0]=n; while(dis[src]!=n) { bool flag=false; for(int &i=head[u];i!=-1;i=next[i]) { int v=G[i].v; int w=G[i].w; if(w&&dis[u]==dis[v]+1) { prev[v]=u; curr[v]=i; flag=true; u=v; break; } } if(flag) { if(u==des) { int cnt=inf; for(int i=des;i!=src;i=prev[i]) { cnt=min(cnt,G[curr[i]].w); } for(int i=des;i!=src;i=prev[i]) { G[curr[i]].w-=cnt; G[curr[i]^1].w+=cnt; } sum+=cnt; u=src; } } else { if(!--gap[dis[u]]) break; else { dis[u]=n; head[u]=pre[u]; for(int i=pre[u];i!=-1;i=next[i]) { int v=G[i].v; int w=G[i].w; if(w) dis[u]=min(dis[u],dis[v]+1); } gap[dis[u]]++; if(u!=src) u=prev[u]; } } } return sum; } int n,m,u,v; int main() { #ifndef ONLINE_JUDGE freopen("飞行员配对方案问题.txt","r",stdin); #else #endif IN(m,n); clear(); FOR(i,1,m) { add(0,i*2,1); add(i*2,i*2+1,1); } FOR(i,m+1,n) { add(i*2,i*2+1,1); add(i*2+1,1,1); } while(IN(u,v),u!=-1||v!=-1) { add(u*2+1,v*2,1); } int ans=SAP(0,1,2*n+2); if(!ans) OL("No Solution!"); else { OL(ans); for(int i=3;2*m+1>=i;i+=2) { ECH(j,i,pre,next) if(!G[j].w) { if(G[j].v>i) OL(i/2,G[j].v/2); } } } return 0; }