HDU1016 Prime Ring Problem

来源：互联网发布：淘宝客怎么做推广计划编辑：程序博客网时间：2024/06/09 12:24

PS: 很基础的一道搜索题目，也不需要特殊的剪枝技术，数据还是挺弱的。

#include <iostream>#include <cstdio>#include <cstring>using namespace std;bool is_prime(int x);void getPrime(); // get Prime.const int maxn = 25;int prime[50]; // save prime.  hash。int res[maxn]; // save result.bool vis[maxn]; // mark if visited.int n;int Case;//Accepted1016250MS300K1392 BG++Achiberxvoid dfs(int parent, int lev)  {    if(lev == n+1 && prime[1+res[n]]==1+res[n] && n>1) {        printf("%d", res[1]);        for(int j = 2; j <= n && n>=2; j++) {            printf(" %d", res[j]);        }        printf("\n");        return;    }    int i;    for(i = 2; i <= n; i++) {        int v = i+parent;        if(!vis[i] && prime[v]==v) {            res[lev] = i;            vis[i] = true;            dfs(i, lev+1);            vis[i] = false;        }    }}int main(){    getPrime();    Case = 1;    while(scanf("%d", &n)!= EOF) {        memset(res, 0, sizeof(res));        memset(vis, false, sizeof(vis));        res[1] = 1;        vis[1] = true;         printf("Case %d:\n", Case++);        dfs(1, 2);// parent, nextIndex.        printf("\n");    }    return 0;}bool is_prime(int x) {    for(int i = 2; i <= x/2; i++) {        if(x%i==0 && x!=i) return false;        continue;    }    return true;}void getPrime() {    for(int i = 2; i <= 45; i++) {        bool ok = is_prime(i);        if(ok){            prime[i] = i;        }        else prime[i] = -1;    }}

0 0