POJ 2060 Taxi Cab Scheme

 

关键在于模型的抽象与理解。

CODE：

#include <iostream>
#include <cstdlib>
#include <cstring>
#include <cstdio>
#include <map>
#include <cmath>
using namespace std;

const int MAXN = 510;

struct node
{
    int costM;
    int tot;
    int x1, y1, x2, y2;
}a[MAXN];

int G[MAXN][MAXN];
int xlink[MAXN], ylink[MAXN];
bool vis[MAXN];
int nx, ny;

void init()
{
    memset(G, 0, sizeof(G));
    memset(xlink, -1, sizeof(xlink));
    memset(ylink, -1, sizeof(ylink));
}

bool ED(int u)
{
    for(int v = 1; v <= ny; v++) if(G[u][v])
    {
        if(!vis[v])
        {
            vis[v] = 1;
            if(ylink[v] == -1 || ED(ylink[v]))
            {
                xlink[u] = v; ylink[v] = u;
                return true;
            }
        }
    }
    return false;
}

void solve()
{
    int ans = 0;
    for(int i = 1; i <= nx; i++)
    {
        if(xlink[i] == -1)
        {
            memset(vis, 0, sizeof(vis));
            ans += ED(i);
        }
    }
    printf("%d\n", nx-ans);
}

void read_case()
{
    init();
    scanf("%d", &nx);
    ny = nx;
    for(int i = 1; i <= nx; i++)
    {
        int h, min, x1, y1, x2, y2;
        scanf("%d:%d %d %d %d %d", &h, &min, &a[i].x1, &a[i].y1, &a[i].x2, &a[i].y2);
        a[i].costM = h*60 + min;
        a[i].tot = a[i].costM + abs(a[i].x1-a[i].x2) + abs(a[i].y1-a[i].y2);
    }
    for(int i = 1; i < nx; i++)
    {
        for(int j = i+1; j <= nx; j++)
        {
            int dif = a[j].costM - a[i].tot;
            int limit = abs(a[j].x1 - a[i].x2) + abs(a[j].y1 - a[i].y2);
            if(dif > limit) G[i][j] = 1;
        }
    }
}

int main()
{
    int T;
    scanf("%d", &T);
    while(T--)
    {
        read_case();
        solve();
    }
    return 0;
}