ZOJ 10th Anniversary Contest - C

水题，DFS+记忆化

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 1 #include<stdio.h>
 2 #include<stdlib.h>
 3 int n,m,s,d,e[105][105],ok[105],cover[105];
 4 int find(int x)
 5 {
 6     int i;
 7     if(ok[x]==1)return 1;
 8     for(i=1;i<=e[x][0];i++)
 9         if(cover[e[x][i]]==0)
10         {
11             cover[e[x][i]]=1;
12             ok[x]=ok[x]|find(e[x][i]);
13             cover[e[x][i]]=0;
14         }
15     return ok[x];
16 }
17 int main()
18 {
19     int i,x,y,ans;
20     while(scanf("%d%d%d%d",&n,&m,&s,&d)!=EOF)
21     {
22        memset(e,0,sizeof(e));
23        memset(ok,0,sizeof(ok));
24        memset(cover,0,sizeof(cover));
25        for(i=1;i<=m;i++)
26        {
27            scanf("%d%d",&x,&y);
28            e[x][0]++;e[x][e[x][0]]=y;
29            e[y][0]++;e[y][e[y][0]]=x;
30        }
31        ok[d]=1;cover[s]=1;
32        find(s);
33        ans=0;
34        for(i=0;i<n;i++)
35            if(ok[i]!=1)ans++;
36        printf("%d\n",ans);
37     }
38     return 0;
39 }