POJ 1129 (dfs)

#include <iostream>
#include <cstdio>
#include <cstring>

using namespace std;

const int M = 30;
int isfind;
int color[M];
int gragh[M][M];
int ans;
int n;

int ok(int id,int x)        //查找相邻的点用的是否用的一个颜色
{
for(int i = 0;i < n; i++) {
if(gragh[id][i] && color[i] == x)
return false;
}
return true;
}

void dfs(int id,int num)
{
if(isfind) return ;
if(id == n) {
isfind = true;
return ;
}
for(int i = 1;i <= num; i++) {
if(ok(id,i)) {
color[id] = i;
dfs(id+1,num);
}
}
if(isfind == 0) {
ans++;
dfs(id,ans);
}
}

int main()
{
//freopen("in.txt","r",stdin);
while(scanf("%d",&n) != EOF && n) {
memset(color,0,sizeof(color));
memset(gragh,0,sizeof(gragh));
for(int i = 0;i < n; i++) {
char s[1000];
scanf("%s",s);
int length = strlen(s);
for(int j = 2;j < length; j++) {
gragh[s[0]-'A'][s[j]-'A'] = true;
}
}
isfind = false;
ans = 1;
dfs(0,1);
if(ans == 1) {
printf("1 channel needed.\n");
}
else {
printf("%d channels needed.\n",ans);
}
}
return 0;
}