zoj 1084 Channel Allocation

#include<stdio.h>#include<string.h>int n,map[27][27],used[27];int dfs(int id,int color){    int i,j,flag;    for(i=1;i<=color;i++)    {        used[id]=i; flag = 1;        for(j=1;j<id;j++)        { if(map[j][id]&&used[j]==used[id]) {     flag = 0;    break; }        }        if(flag && (id == n || dfs(id+1,color))) return 1;    }    return 0;}int main(){    char str[30];    int i,j,one;    while(scanf("%d",&n)!=EOF&&n)    {        one = 1;        memset(map,0,sizeof(map));        for(i=1;i<=n;i++)        { scanf("%s",str); for(j=2;str[j];j++,one = 0)     map[i][str[j]-'A'+1] = map[str[j]-'A'+1][i] = 1;        }        used[1]=1;        if(one)    printf("1 channel needed.n");        else if(dfs(2,2))    printf("2 channels needed.n");        else if(dfs(2,3))    printf("3 channels needed.n");        else printf("4 channels needed.n");    }    return 0;}