题目大意:给定一个4位素数,一个目标4位素数.每次变换一位,保证变换后依然是素数,求变换到目标素数的最小步数. 解题报告:直接用最短路. 枚举1000-10000所有素数,如果素数A交换一位可以得到素数B,则在AB间加入一条长度为1的双向边. 则题中所求的便是从起点到终点的最短路.使用Dijkstra或SPFA皆可. 当然,纯粹的BFS也是可以的. 用Dijkstra算法A了题目之后,看了一下Discuss,发现了一个新名词,双向BFS. 即从起点和终点同时进行BFS,相遇则求得最短路. 借鉴了…

  POJ 3126  Prime Path Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 16204   Accepted: 9153 Description The ministers of the cabinet were quite upset by the message from the Chief of Security stating that they would all have to change…

题目传送门 /* 题意:从一个数到另外一个数,每次改变一个数字,且每次是素数 BFS:先预处理1000到9999的素数,简单BFS一下.我没输出Impossible都AC,数据有点弱 */ /************************************************ Author :Running_Time Created Time :2015-8-2 15:46:57 File Name :POJ_3126.cpp ****************************…

POJ 3126 Prime Path(素数路径) Time Limit: 1000MS    Memory Limit: 65536K Description - 题目描述 The ministers of the cabinet were quite upset by the message from the Chief of Security stating that they would all have to change the four-digit room numbers on…

题目链接:http://poj.org/problem?id=3126 Prime Path Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 32036   Accepted: 17373 Description The ministers of the cabinet were quite upset by the message from the Chief of Security stating that they…

Prime Path POJ - 3126 题意: 给出两个四位素数 a , b.然后从a开始,每次可以改变四位中的一位数字,变成 c,c 可以接着变,直到变成b为止.要求 c 必须是素数.求变换次数的最小值.(a,b,c都是四位数字,输入时没有前导零) 分析: 每次改变可以获得一个四位数c,然后如果c是素数并且之前没有出现过,那么我们把它放入队列即可. int f[10001]; int v[10001]; void init()//素数筛 { memset(f,0,sizeof f); fo…

题目: http://poj.org/problem?id=3126 困得不行了,没想到敲完一遍直接就A了,16ms,debug环节都没进行.人品啊. #include <stdio.h> #include <string.h> #include <queue> using namespace std; ]; ]; int s, t; void prime_init() { memset(prime, , sizeof(prime)); prime[] = ; ; i…

意甲冠军  给你两个4位质数a, b  每次你可以改变a个位数,但仍然需要素数的变化  乞讨a有多少次的能力,至少修改成b 基础的bfs  注意数的处理即可了  出队一个数  然后入队全部能够由这个素数经过一次改变而来的素数  知道得到b #include <cstdio> #include <cstring> using namespace std; const int N = 10000; int p[N], v[N], d[N], q[N], a, b; void initP…

Description The ministers of the cabinet were quite upset by the message from the Chief of Security stating that they would all have to change the four-digit room numbers on their offices. — It is a matter of security to change such things every now…

Prime Path Time Limit: 1000MS Memory Limit: 65536K Total Submissions: 26475 Accepted: 14555 Description The ministers of the cabinet were quite upset by the message from the Chief of Security stating that they would all have to change the four-digit…