POJ3126 Prime Path（BFS） 类似于Leetcode 单词接龙

Leetcode 单词接龙问题传送门：https://leetcode-cn.com/problems/word-ladder/

Sample Input
3
1033 8179
1373 8017
1033 1033
Sample Output
6
7
0

题目解释
给定两个素数，求出从起始数到终点数的最短替换数字次数。替换方式为：每次只能替换一个数字，替换过程中的所有数字也必须都是素数。

注意： 1000以下的素数被忽略了，否则从1373 -> 8017应该是5步
但是我十分怀疑测试数据中有小于1000 的数，我尝试打表1000-9999的素数之后bfs，结果总是wa，和正确代码比较结果也没有发现问题，只是我的代码在输入1000以下的数字时会输出Impossible。
（说实话我觉得我打表的方法如果能过的话时间空间复杂度都比现去判断素数要好很多…毕竟只开一个一千左右的数组就够了…全判断得开一万的）

我的代码（WA） （如果有大佬能看出为什么WA的话跪求指点！）

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <queue> 
#include <cstring>

using namespace std;

int prime[1075] = {1009,1013,1019,1021,1031,1033,1039,1049,1051,1061,1063,1069,1087,1091,1093,1097,1103,1109,1117,1123,1129,1151,1153,1163,1171,1181,1187,1193,1201,1213,1217,1223,1229,1231,1237,1249,1259,1277,1279,1283,1289,1291,1297,1301,1303,1307,1319,1321,1327,1361,1367,1369,1373,1381,1399,1409,1423,1427,1429,1433,1439,1447,1451,1453,1459,1471,1481,1483,1487,1489,1493,1499,1511,1523,1531,1543,1549,1553,1559,1567,1571,1579,1583,1597,1601,1607,1609,1613,1619,1621,1627,1637,1657,1663,1667,1669,1681,1693,1697,1699,1709,1721,1723,1733,1741,1747,1753,1759,1777,1783,1787,1789,1801,1811,1823,1831,1847,1849,1861,1867,1871,1873,1877,1879,1889,1901,1907,1913,1931,1933,1949,1951,1973,1979,1987,1993,1997,1999,2003,2011,2017,2027,2029,2039,2053,2063,2069,2081,2083,2087,2089,2099,2111,2113,2129,2131,2137,2141,2143,2153,2161,2179,2203,2207,2209,2213,2221,2237,2239,2243,2251,2267,2269,2273,2281,2287,2293,2297,2309,2311,2333,2339,2341,2347,2351,2357,2371,2377,2381,2383,2389,2393,2399,2411,2417,2423,2437,2441,2447,2459,2467,2473,2477,2503,2521,2531,2539,2543,2549,2551,2557,2579,2591,2593,2609,2617,2621,2633,2647,2657,2659,2663,2671,2677,2683,2687,2689,2693,2699,2707,2711,2713,2719,2729,2731,2741,2749,2753,2767,2777,2789,2791,2797,2801,2803,2809,2819,2833,2837,2843,2851,2857,2861,2879,2887,2897,2903,2909,2917,2927,2939,2953,2957,2963,2969,2971,2999,3001,3011,3019,3023,3037,3041,3049,3061,3067,3079,3083,3089,3109,3119,3121,3137,3163,3167,3169,3181,3187,3191,3203,3209,3217,3221,3229,3251,3253,3257,3259,3271,3299,3301,3307,3313,3319,3323,3329,3331,3343,3347,3359,3361,3371,3373,3389,3391,3407,3413,3433,3449,3457,3461,3463,3467,3469,3481,3491,3499,3511,3517,3527,3529,3533,3539,3541,3547,3557,3559,3571,3581,3583,3593,3607,3613,3617,3623,3631,3637,3643,3659,3671,3673,3677,3691,3697,3701,3709,3719,3721,3727,3733,3739,3761,3767,3769,3779,3793,3797,3803,3821,3823,3833,3847,3851,3853,3863,3877,3881,3889,3907,3911,3917,3919,3923,3929,3931,3943,3947,3967,3989,4001,4003,4007,4013,4019,4021,4027,4049,4051,4057,4073,4079,4091,4093,4099,4111,4127,4129,4133,4139,4153,4157,4159,4177,4201,4211,4217,4219,4229,4231,4241,4243,4253,4259,4261,4271,4273,4283,4289,4297,4327,4337,4339,4349,4357,4363,4373,4391,4397,4409,4421,4423,4441,4447,4451,4457,4463,4481,4483,4489,4493,4507,4513,4517,4519,4523,4547,4549,4561,4567,4583,4591,4597,4603,4621,4637,4639,4643,4649,4651,4657,4663,4673,4679,4691,4703,4721,4723,4729,4733,4751,4759,4783,4787,4789,4793,4799,4801,4813,4817,4831,4861,4871,4877,4889,4903,4909,4919,4931,4933,4937,4943,4951,4957,4967,4969,4973,4987,4993,4999,5003,5009,5011,5021,5023,5039,5041,5051,5059,5077,5081,5087,5099,5101,5107,5113,5119,5147,5153,5167,5171,5179,5189,5197,5209,5227,5231,5233,5237,5261,5273,5279,5281,5297,5303,5309,5323,5329,5333,5347,5351,5381,5387,5393,5399,5407,5413,5417,5419,5431,5437,5441,5443,5449,5471,5477,5479,5483,5501,5503,5507,5519,5521,5527,5531,5557,5563,5569,5573,5581,5591,5623,5639,5641,5647,5651,5653,5657,5659,5669,5683,5689,5693,5701,5711,5717,5737,5741,5743,5749,5779,5783,5791,5801,5807,5813,5821,5827,5839,5843,5849,5851,5857,5861,5867,5869,5879,5881,5897,5903,5923,5927,5939,5953,5981,5987,6007,6011,6029,6037,6043,6047,6053,6067,6073,6079,6089,6091,6101,6113,6121,6131,6133,6143,6151,6163,6173,6197,6199,6203,6211,6217,6221,6229,6241,6247,6257,6263,6269,6271,6277,6287,6299,6301,6311,6317,6323,6329,6337,6343,6353,6359,6361,6367,6373,6379,6389,6397,6421,6427,6449,6451,6469,6473,6481,6491,6521,6529,6547,6551,6553,6563,6569,6571,6577,6581,6599,6607,6619,6637,6653,6659,6661,6673,6679,6689,6691,6701,6703,6709,6719,6733,6737,6761,6763,6779,6781,6791,6793,6803,6823,6827,6829,6833,6841,6857,6863,6869,6871,6883,6889,6899,6907,6911,6917,6947,6949,6959,6961,6967,6971,6977,6983,6991,6997,7001,7013,7019,7027,7039,7043,7057,7069,7079,7103,7109,7121,7127,7129,7151,7159,7177,7187,7193,7207,7211,7213,7219,7229,7237,7243,7247,7253,7283,7297,7307,7309,7321,7331,7333,7349,7351,7369,7393,7411,7417,7433,7451,7457,7459,7477,7481,7487,7489,7499,7507,7517,7523,7529,7537,7541,7547,7549,7559,7561,7573,7577,7583,7589,7591,7603,7607,7621,7639,7643,7649,7669,7673,7681,7687,7691,7699,7703,7717,7723,7727,7741,7753,7757,7759,7789,7793,7817,7823,7829,7841,7853,7867,7873,7877,7879,7883,7901,7907,7919,7921,7927,7933,7937,7949,7951,7963,7993,8009,8011,8017,8039,8053,8059,8069,8081,8087,8089,8093,8101,8111,8117,8123,8147,8161,8167,8171,8179,8191,8209,8219,8221,8231,8233,8237,8243,8263,8269,8273,8287,8291,8293,8297,8311,8317,8329,8353,8363,8369,8377,8387,8389,8419,8423,8429,8431,8443,8447,8461,8467,8501,8513,8521,8527,8537,8539,8543,8563,8573,8581,8597,8599,8609,8623,8627,8629,8641,8647,8663,8669,8677,8681,8689,8693,8699,8707,8713,8719,8731,8737,8741,8747,8753,8761,8779,8783,8803,8807,8819,8821,8831,8837,8839,8849,8861,8863,8867,8887,8893,8923,8929,8933,8941,8951,8963,8969,8971,8999,9001,9007,9011,9013,9029,9041,9043,9049,9059,9067,9091,9103,9109,9127,9133,9137,9151,9157,9161,9173,9181,9187,9199,9203,9209,9221,9227,9239,9241,9257,9277,9281,9283,9293,9311,9319,9323,9337,9341,9343,9349,9371,9377,9391,9397,9403,9409,9413,9419,9421,9431,9433,9437,9439,9461,9463,9467,9473,9479,9491,9497,9511,9521,9533,9539,9547,9551,9587,9601,9613,9619,9623,9629,9631,9643,9649,9661,9677,9679,9689,9697,9719,9721,9733,9739,9743,9749,9767,9769,9781,9787,9791,9803,9811,9817,9829,9833,9839,9851,9857,9859,9871,9883,9887,9901,9907,9923,9929,9931,9941,9949,9967,9973};
int visited[1075]; 

bool canvisit(int from,int to){
	int counter =0;
	for(int i=0;i<4;i++)
	{
		if((from%10)!=(to%10))
			counter++;
		from = from/10;
		to = to/10;
	}
	
	if(counter!=1)
		return false;
	return true;
}

int main()
{
	for(int i=0;i<50;i++)
	{
		cout << prime[rand()*1075/RAND_MAX]<<endl;
	 } 
	int counter;
	scanf("%d",&counter);
	int m,n;
	for(int time = 0;time<counter;time++)
	{
		scanf("%d %d",&m,&n);
		if(m==n)
		{
			cout << "0" << endl;
			continue;
		}
		memset(visited,0,1075*sizeof(int));
		queue<pair<int,int> > tempQueue;
		tempQueue.push({m,0});
		bool found = false;
		while(!tempQueue.empty())
		{
			pair<int,int> tempPair = tempQueue.front();
			tempQueue.pop();
			for(int i=0;i<1075;i++)
			{
				if(visited[i]==0 && canvisit(tempPair.first,prime[i]))
				{
					if(prime[i]==n)
					{
						cout << tempPair.second+1 << endl;
						found = true;
						break;
					}
					visited[i]=1;
					tempQueue.push({prime[i],tempPair.second+1});
				}
			}
			if(found)
				break;
		}
		if(!found)
			cout <<"Impossible"<<endl;
	}

	return 0;
 } 

正确代码：
来自 https://blog.csdn.net/weixin_44339734/article/details/104174521

#include<iostream>
#include<cmath>
#include<queue>
#include<cstdio>
#include <cstring>
#include<stdlib.h>
using namespace std;
bool is_prime[10005];
const int INF = 1e5;
int cnt[10005];
int visit[10005];

void init(int a, int b)	//初始化
{
    memset(visit, 0, sizeof(visit));
    for (int i = 0; i <= 10005; i++)
    {
        cnt[i] = INF;
    }
    cnt[a] = 0;	//到本身的次数为0
}
void sieve(int b)	//埃氏筛
{
    for (int i = 2; i <= b; i++)
        is_prime[i] = true;
    for (int i = 2; i <= b; i++)
        if (is_prime[i])
            for (int j = i * 2; j <= b; j += i)
                is_prime[j] = false;
}

void bfs(int a, int b)
{
    if (a == b)return;
    queue<int> q;
    q.push(a);
    visit[a] = 1;
    while (!q.empty())
    {
        int val = q.front();
        int t = val;
        q.pop();
        int num[4];
        for (int i = 3; i >= 0; i--)
        {
            int left = t % 10;
            num[i] = left;
            t /= 10;
        }
        for (int i = 0; i < 4; i++)	//表示位数
        {
            int temp = num[i];	//暂存
            for (int j = 0; j < 10; j++)	//表示变换数字
            {
                if (i == 0 && j == 0)continue;	//排除掉前导0
                num[i] = j;
                int next = num[0] * 1000 + num[1] * 100 + num[2] * 10 + num[3];	//一步变换得到的数
                if (is_prime[next] && !visit[next] && cnt[next] > 1 + cnt[val])	//求解
                {
                    cnt[next] = 1 + cnt[val];
                    q.push(next);
                    visit[next] = 1;
                }
            }
            num[i] = temp;
        }
    }
}

int main()
{
    int a, b;
    int n;
    scanf("%d", &n);
    sieve(10001);	//先求出10000内的素数
    while (n--)
    {
        scanf("%d%d", &a, &b);
        init(a, b);	//初始化
        bfs(a, b);	//搜索问题的解
        if (cnt[b] != INF)printf("%d\n", cnt[b]);
        else printf("Impossible\n");
    }
    return 0;
}