Uva 1572 自组合

贴个源码
// UVa1572 Self-Assembly
// Rujia Liu
#include<cstdio>
#include<cstring>
#include<vector>
using namespace std;

int ID(char a1, char a2) {
  return (a1-'A')* + (a2 == '+' ?  : );
}

int G[][];

// connect(A+, B-) means a border labeled with A- can be transformed to B-
void connect(char a1, char a2, char b1, char b2) {
  if(a1 == '' || b1 == '') return;
  int u = ID(a1, a2)^, v = ID(b1, b2);
  G[u][v] = ;
}

int c[];

// returns true iff there is a cycle reachable from u
bool dfs(int u) {
  c[u] = -;
  for(int v = ; v < ; v++) if(G[u][v]) {
    if(c[v] < ) return true;
    else if(!c[v] && dfs(v)) return true;
  }
  c[u] = ;
  return false;
}

bool find_cycle() {
  memset(c, , sizeof(c));
  for(int i = ; i < ; i++) if(!c[i])
    if(dfs(i)) return true;
  return false;
}

int main() {
  int n;
  while(scanf("%d", &n) ==  && n) {
    memset(G, , sizeof(G));
    while(n--) {
      char s[];
      scanf("%s", s);
      for(int i = ; i < ; i++)
        for(int j = ; j < ; j++) if(i != j)
          connect(s[i*], s[i*+], s[j*], s[j*+]);
    }
    if(find_cycle()) printf("unbounded\n");
    else printf("bounded\n");
  }
  return ;
}