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')*2 + (a2 == '+' ? 0 : 1);
}

int G[52][52];

// 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 == '0' || b1 == '0') return;
  int u = ID(a1, a2)^1, v = ID(b1, b2);
  G[u][v] = 1;
}

int c[52];

// returns true iff there is a cycle reachable from u
bool dfs(int u) {
  c[u] = -1;
  for(int v = 0; v < 52; v++) if(G[u][v]) {
    if(c[v] < 0) return true;
    else if(!c[v] && dfs(v)) return true;
  }
  c[u] = 1;
  return false;
}

bool find_cycle() {
  memset(c, 0, sizeof(c));
  for(int i = 0; i < 52; i++) if(!c[i])
    if(dfs(i)) return true;
  return false;
}

int main() {
  int n;
  while(scanf("%d", &n) == 1 && n) {
    memset(G, 0, sizeof(G));
    while(n--) {
      char s[10];
      scanf("%s", s);
      for(int i = 0; i < 4; i++)
        for(int j = 0; j < 4; j++) if(i != j)
          connect(s[i*2], s[i*2+1], s[j*2], s[j*2+1]);
    }
    if(find_cycle()) printf("unbounded
");
    else printf("bounded
");
  }
  return 0;
}