hdu 5487 Difference of Languages（bfs）

解题思路

代码

#include <cstdio>
#include <cstring>
#include <algorithm>

using namespace std;
const int maxn = 1005;
const int maxm = 26;

struct DFA {
int n, g[maxn][maxm];
bool ac[maxn];

void init () {
int m, k, u, v;
char c[5];
scanf("%d%d%d", &n, &m, &k);

memset(ac, false, sizeof(ac));
for (int i = 0; i <= n; i++)
for (int j = 0; j < maxm; j++) g[i][j] = n;

while (k--) {
scanf("%d", &u);
ac[u] = true;
}

while (m--) {
scanf("%d%d%s", &u, &v, c);
g[u][c[0]-'a'] = v;
}
}
}A, B;

struct State {
int u, v, p, w;
State (int u = 0, int v = 0, int p = 0, int w = 0): u(u), v(v), p(p), w(w) {}
}Q[maxn * maxn];

bool vis[maxn][maxn];

void put (int x) {
if (x > 0) {
put(Q[x].p);
printf("%c", Q[x].w + 'a');
}
}

bool solve () {
if (A.ac[0]^B.ac[0]) return true;

memset(vis, false, sizeof(vis));
int head = 0, rear = 0;

Q[rear++] = State(0, 0, -1, 0);
vis[0][0] = true;

while (head < rear) {
State& cur = Q[head++];

for (int i = 0; i < maxm; i++) {
int u = A.g[cur.u][i];
int v = B.g[cur.v][i];
if (vis[u][v]) continue;
vis[u][v] = true;
Q[rear++] = State(u, v, head-1, i);

if (A.ac[u]^B.ac[v]) {
put(rear-1);
return true;
}
}
}
return false;
}

int main () {
int cas;
scanf("%d", &cas);
for (int kcas = 1; kcas <= cas; kcas++) {
A.init();
B.init();
printf("Case #%d: ", kcas);
if (!solve()) printf("0\n");
else printf("\n");
}
return 0;
}