poj 3126 Prime Path （bfs)

#include<iostream>
#include<queue>
#include<cstring>
#include<cstdlib>
#include<cmath>

using namespace std;
int n;
int prime[10010] = {0};
int book[10010];
int step[10010];

int bfs(int sou, int des) {
queue<int> q;
memset(book, 0, sizeof(book));
memset(step, 0, sizeof(step));
q.push(sou);
book[sou] = 1;
while(!q.empty()) {
int x = q.front();
q.pop();
int t[4];
t[0] = x / 1000;
t[1] = x % 1000 / 100;
t[2] = x % 100 / 10;
t[3] = x % 10;
int i, j, tmp;
for(i = 0; i < 4; i++) {
tmp = t[i];
for(j = 0; j < 10; j++) {
if(tmp != j) {
t[i] = j;
int y = t[3] + t[2] * 10 + t[1] * 100 + t[0] * 1000;
if(!book[y] && prime[y]) {
q.push(y);
step[y] = step[x] + 1;
book[y] = 1;
}
if(y == des) return step[y];
}
}
t[i] = tmp;
}
if(x == des) return step[x];
}
return -1;
}

int main() {
prime[0] = prime[1] = 1;
int i, j;
for(i = 0; i < 10010; i++) {
prime[i] = 1;
}
for(i = 2; i <= sqrt(10010.0); i++) {
if(prime[i]) {
for(j = i + i; j < 10010; j += i) {
prime[j] = 0;
}
}
}
for(i = 0; i < 1000; i++) {
prime[i] = 0;
}
cin >> n;
while(n--) {
int a, b;
cin >> a >> b;
int t = bfs(a, b);
if(t == -1) cout << "Impossible" << endl;
else cout << t << endl;
}
return 0;
}

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <queue>
#include <cmath>
using namespace std;
int isprime[10010];
int vis[10010];
void init() {
int i, j;
for(i = 0; i < 10000; i++) {
isprime[i] = 1;
}
isprime[0] = isprime[1] = 0;
for(i = 2; i <= sqrt(10000); i++) {
if(isprime[i] == 1) {
for(j = i + i; j < 10000; j += i) {
isprime[j] = 0;
}
}
}
for(i = 0; i <= 999; i++) {
isprime[i] = 0;
}
}
int a, b;
struct node {
int num, step;
};
int bfs() {
queue<node> q;
node now, next;
now.num = a, now.step = 0;
q.push(now);
vis[now.num] = 1;
while(!q.empty()) {
now = q.front();
q.pop();
int i, j;
if(now.num == b) {
return now.step;
}
for(i = 0; i < 4; i++) {
for(j = 0; j <= 9; j++) {
if(now.num % (int)pow(10, i + 1) / (int)pow(10, i) == j) continue;
int t1 = now.num / (int)pow(10, i + 1);
int t2 = now.num % (int)pow(10, i);
next.num = t1 * (int)pow(10, i + 1) + j * (int)pow(10, i) + t2;
next.step = now.step + 1;
if(vis[next.num] == 0 && isprime[next.num] == 1) {
vis[next.num] = 1;
q.push(next);
}
}
}
}
return -1;
}
int main() {
init();
int n;
scanf("%d", &n);
while(n--) {
memset(vis, 0, sizeof(vis));
scanf("%d %d", &a, &b);
printf("%d\n", bfs());
}
return 0;
}