hdu 2094拓扑排序map实现记录

#include<stdio.h>

#include<iostream>

#include<algorithm>

#include<string>

#include<string.h>

#include<stdlib.h>

#define N 1100

#include<map>

using namespace std;

int pre[N],indegree[N];

int find(int x) {

if(pre[x]!=x)

pre[x]=find(pre[x]);

return pre[x];

}

int judge(int n) {

int  k=0,i;

for(i=1;i<=n;i++)

if(indegree[i]==0)

k++;

if(k==1)

return 1;

return 0;

}

map<string,int>p;

int main() {

int n,i,j,h,ans;

char s[N];

while(scanf("%d",&n),n) {

  p.clear();

memset(indegree,0,sizeof(indegree));

for(i=1;i<N;i++)

pre[i]=i;

h=0;

while(n--) {

scanf("%s",s);

if(p.find(s)==p.end())

p[s]=++h;

i=p[s];

scanf("%s",s);

if(p.find(s)==p.end())

p[s]=++h;

j=p[s];

pre[find(i)]=pre[find(j)];

indegree[j]++;

}

ans=0;

for(i=1;i<=h;i++)

if(find(i)==i)

ans++;

if(judge(h)&&ans==1) 

printf("Yes\n");

else

printf("No\n");

}

return 0;

}