POJ3126Prime Path

一. 题目链接：http://poj.org/problem?id=3126

二. 一看就知道广搜，然后还耗费了2个多小时才AC，中间还贡献了一次TLE（忘记标记走过路径）。还看了几天前的博客，好像就是2天前，才记得怎么求最短路径-  -！

三. 代码：

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

using namespace std;

const int MAX_SIZE = 9999;
struct node
{
    int arr[5];
    int time;
    friend bool operator < (node a, node b) { return a.time > b.time;  }
};

bool primeList[MAX_SIZE + 6];
node start, finish;
bool visited[MAX_SIZE + 1];

void numToArr(int num, int *arr)
{
    for(int i = 4; i > 0; i--){
        arr[i] = num%10;
        num = num/10;
    }
}

int ArrToNum(int *arr)
{
    int ans = 0;
    for(int i = 1; i <= 4; i++)
        ans += arr[i]*pow(10, 4-i);
    return ans;
}

void buildList()
{
    int i, j, nsqrt = sqrt(MAX_SIZE) + 1;
    memset(primeList, 0, sizeof(primeList));

    for(i = 2; i <= nsqrt; i++)
        for(j = 2; j <= MAX_SIZE/i; j++)
            primeList[j*i] = true;
}

int bfs()
{
    priority_queue <node> que;
    node cur, Next;
    int i, j, t;
    que.push(start);
    visited[ArrToNum(start.arr)] = true;

    while(!que.empty()){
        cur = que.top();
        que.pop();
        if(ArrToNum(cur.arr) == ArrToNum(finish.arr))
            return cur.time;

        for(i = 1; i <= 4; i++){
            for(j = 0; j < 10; j++){
                if(j == cur.arr[i] || 1 == i && 0 == j)
                    continue;

                for(t = 1; t <= 4; t++)
                    if(t != i)
                        Next.arr[t] = cur.arr[t];
                    else
                        Next.arr[t] = j;
                if(visited[i])
                    continue;

                if(primeList[ArrToNum(Next.arr)])
                    continue;

                if(visited[ArrToNum(Next.arr)])
                    continue;
                else
                    visited[ArrToNum(Next.arr)] = true;

                Next.time = cur.time + 1;
                que.push(Next);
            }
        }
    }
    return -1;
}

int main()
{
    //freopen("in.txt", "r", stdin);
    buildList();
    int T, startNumber, finishNumber;

    cin>>T;
    while(T--){
        cin>>startNumber>>finishNumber;

        numToArr(startNumber, start.arr);
        numToArr(finishNumber, finish.arr);
        start.time = 0;
        memset(visited, 0, sizeof(visited));

        int ans = bfs();
        if(ans == -1)
            cout<<"Impossible"<<endl;
        else
            cout<<ans<<endl;

    }

    return 0;
}