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  • DFS专题 Prime Ring Problem

    View Code
    # include <cstdio>
    # include <cstring>
    
    # define N 20 + 5
    
    char ptab[25] = {0, 0, 1, 1, 0,
                           1, 0, 1, 0, 0,
                           0, 1, 0, 1, 0,
                           0, 0, 1, 0, 1,
                           0, 0, 0, 1, 0};
    
    int n, solu[N];
    bool vis[N];
    
    void dfs(int cnt)
    {
        if (cnt == n && ptab[solu[cnt]+1])
        {
            printf("1");
            for (int i = 2; i <= n; ++i)
                printf(" %d", solu[i]);
            putchar('\n');
            return ;
        }
        for (int i = 2; i <= n; ++i)
        {
            if (vis[i] == false && ptab[solu[cnt]+i])
            {
                vis[i] = true;
                solu[cnt+1] = i;
                dfs(cnt+1);
                vis[i] = false;
            }
        }
    }
    
    void solve(void)
    {
        solu[1] = 1, vis[1] = true;
        memset(vis+1, false, sizeof(vis[0])*n);
        dfs(1);
        putchar('\n');
    }
    
    int main()
    {
        int i = 0;
    
        while (~scanf("%d", &n))
        {
            printf("Case %d:\n", ++i);
            solve();
        }
    
        return 0;
    }

     

    Problem Description

    A ring is compose of n circles as shown in diagram. Put natural number 1, 2, ..., n into each circle separately, and the sum of numbers in two adjacent circles should be a prime.

    Note: the number of first circle should always be 1.


    Input

    n (0 < n < 20).

    Output

    The output format is shown as sample below. Each row represents a series of circle numbers in the ring beginning from 1 clockwisely and anticlockwisely. The order of numbers must satisfy the above requirements. Print solutions in lexicographical order.

    You are to write a program that completes above process.

    Print a blank line after each case.

    Sample Input

    6
    8
    

    Sample Output

    Case 1:
    1 4 3 2 5 6
    1 6 5 2 3 4
    
    Case 2:
    1 2 3 8 5 6 7 4
    1 2 5 8 3 4 7 6
    1 4 7 6 5 8 3 2
    1 6 7 4 3 8 5 2
    
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  • 原文地址:https://www.cnblogs.com/JMDWQ/p/2597966.html
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