UVA 524 (Prime ring)

Description

A Ring is composed of n (even number) circles as shown in diagram. Put natural numbers into each circle separately, and the sum of numbers in both adjacent circles should be a prime.

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

Input N (0 < n <=) OutputThe 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.

You is to write a program, that completes above process.

Sample Input

68

Sample Output

Case 1:1 4 3 2 5 a 6 5 2 3 4Case 2:1 2 3 8 5 6 7 41 2 5 8 3 4 7 61 4 7 6 5 8 3 21 6 7 4 3 8 5 2

Miguel A. Revilla
1999-01-11Test instructionsEnter a positive integer n, the 1,2,3,...,n is composed of a ring, so that the sum of the adjacent two positive numbers are prime, the output at the beginning of the integer 1 counter-clockwise, the same ring exactly output once.Ideas:Use DFS for backtracking.Code:

#include <cstdio> #include <algorithm>using namespace Std;int s[20];int main () {    int n,casex=1;    Long long ans,a;    while (scanf ("%d", &n)!=eof)    {       ans=0;        for (int i=1;i<=n;i++)            scanf ("%d", &s[i]);        for (int i=1;i<=n;i++)        {for            (int j=i;j<=n;j++)            {                    a=1;                for (int k=i;k<=j;k++)                {                    a*=s[k];                }                Ans=max (ans,a);            }        }            printf ("Case #%d:the maximum product is%lld.\n\n", Casex,ans);            casex++;    }    return 0;}

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UVA 524 (Prime ring)