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Forming Quiz Teams

                        Forming Quiz Teams

                                                      dp + bitmasking

Problem Link 


#include <iostream>
#include <cstdio>
#include <math.h>
#include <cstring>

#define sf(a) scanf("%d", &a)
#define REP(i, n) for(int i = 0; i < n; i++)

using namespace std;

int n, posx, posy;
char name[21];

double dist[17][17];
double dp[1 << 16];
int xy[17][2];

double solve(int bits)
{

    if(dp[bits] != -1)
        return dp[bits];

    if(bits == (1 << n) - 1)
        return 0;

    double ans = 1 << 30; // random big number

    for(int i = 0; i < n; i++)
    {
        if(!(bits & (1 << i)))
        {
            for(int j = i + 1; j < n; j++)
            {
                if(!(bits & (1 << j)))
                {
                    ans = min(ans, solve(bits | (1 << i) | (1 << j)) + dist[i][j]);
                }

            }
        }

    }

    return dp[bits] = ans;
}

int main()
{
    int k = 1;
    while(true)
    {
        sf(n);
        if(n == 0)
            break;

        n = 2 * n;

        REP(i, n)
        {
            scanf("%s", name);
            sf(posx);
            sf(posy);

            xy[i][0] = posx;
            xy[i][1] = posy;
        }

        for(int i = 0; i < n; i++)
        {
            for(int j = i + 1; j < n; j++)
            {
                double x = (xy[i][0] - xy[j][0]) * (xy[i][0] - xy[j][0]);
                double y = (xy[i][1] - xy[j][1]) * (xy[i][1] - xy[j][1]);

                dist[i][j] =  dist[j][i] = sqrt(x + y);
            }
        }

        for(int i = 0; i < (1 << 16); i++)
        {
            dp[i] = -1;
        }

        double ans = solve(0);
        printf("Case %d: %.2f\n",k++, ans);
    }
    return 0;
}

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