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题目链接： [

https://icpcarchive.ecs.baylor.edu/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=1127
](https://icpcarchive.ecs.baylor.edu/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=1127)

DAG最小路径覆盖 = 点数 - 最大匹配数。

代码:

#include <stdio.h>
#include <ctime>
#include <math.h>
#include <limits.h>
#include <complex>
#include <string>
#include <functional>
#include <iterator>
#include <algorithm>
#include <vector>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <list>
#include <bitset>
#include <sstream>
#include <iomanip>
#include <fstream>
#include <iostream>
#include <ctime>
#include <cmath>
#include <cstring>
#include <cstdio>
#include <time.h>
#include <ctype.h>
#include <string.h>
#include <assert.h>

using namespace std;

int n;
int p[510][510];
int book[510];
int match[510];
bool vis[510];

bool dfs(int u)
{
    for (int i = 1; i <= n; i++)
    {
        if (book[i] == 0 && p[u][i] == 1)
        {
            book[i] = 1;
            if (match[i] == 0 || dfs(match[i]))
            {
                match[i] = u;
                return true;
            }
        }
    }
    return false;
}

struct node
{
    int x1, y1, x2, y2;
    int st, ed;
}taxi[510];

int get_dis(node a, node b)
{
    return abs(a.x2 - b.x1) + abs(a.y2 - b.y1);
}

int main()
{
    int t;
    scanf("%d", &t);
    while (t--)
    {
        memset(p, 0, sizeof(p));
        memset(match, 0, sizeof(match));
        memset(vis, false, sizeof(vis));

        scanf("%d", &n);
        int a, b, c, d, e, f;
        char s[10];
        for (int i = 1;i <= n;i++)
        {
            scanf("%s %d %d %d %d", s, &c, &d, &e, &f);
            a = (s[0] - '0') * 10 + (s[1] - '0');
            b = (s[3] - '0') * 10 + (s[4] - '0');
        //  printf("        %d %d %d %d %d %d\n", a, b, c, d, e, f);
            taxi[i].st = a * 60 + b;
            taxi[i].ed = taxi[i].st + abs(c - e) + abs(d - f);
            taxi[i].x1 = c;
            taxi[i].y1 = d;
            taxi[i].x2 = e;
            taxi[i].y2 = f;
        }

        for (int i = 1;i <= n;i++)
            for (int j = 1;j <= n;j++)
            {
                if (taxi[i].ed + get_dis(taxi[i],taxi[j]) < taxi[j].st)
                    p[i][j] = 1;
            }
        int ans = 0;
        for (int i = 1; i <= n; i++)
        {
            memset(book, 0, sizeof(book));
            if (dfs(i))
                ans++;
        }
        printf("%d\n", n - ans);
    }
    return 0;
}