HDU 1181 变形课

#include <bits/stdc++.h>
using namespace std;

const int maxn = 30;
int g[maxn][maxn];
char s[100000];
int len;

/*
  g[i][j] == 0 (i -> j 走不通)
  g[i][j] == 1 (i -> j 可以走)
*/

void bfs() {
  int flag[30];
  for(int i = 0; i < 26; i ++) {
    flag[i] = 0;
  }
  queue<int> Q;
  Q.push(1);
  flag[1] = 1;
  while(!Q.empty()) {
    int t = Q.front();
    Q.pop();
    for(int i = 0; i < 26; i ++) {
      if(g[t][i] && flag[i] == 0) {
        Q.push(i);
        flag[i] = 1;
      }
    }
  }

  if(flag[‘m‘ - ‘a‘]) {
    printf("Yes.\n");
  } else {
    printf("No.\n");
  }
}

int main() {
    while(~scanf("%s", s)) {
      len = strlen(s);
      if(len == 1 && s[0] == ‘0‘) {
        bfs();
        memset(g, 0, sizeof g);
        continue;
      }
      g[s[0] - ‘a‘][s[len - 1] - ‘a‘] = 1;
    }
    return 0;
}