HDU 2389 Rain on your Parade（Hopcroft_Carp Algorithm）

题目链接：
HDU 2389 Rain on your Parade

#include <cstdio>
#include <cstring>
#include <cmath>
#include <iostream>
#include <string>
#include <algorithm>
#include <climits>
#include <queue>
using namespace std;
const int MAX_N = 3010;

int T, n, m, total, dis, cases = 0;
double t, x[MAX_N], y[MAX_N], v[MAX_N];
int matchx[MAX_N], matchy[MAX_N], head[MAX_N];
int disx[MAX_N],disy[MAX_N], vis[MAX_N];

struct Edge{
    int to, next;

    Edge () {}
    Edge(int _to, int _next) : to(_to), next(_next) {
    }
}edge[MAX_N*MAX_N];

inline void init()
{
    total=0;
    memset(matchx,-1,sizeof(matchx));
    memset(matchy,-1,sizeof(matchy));
    memset(head,-1,sizeof(head));
}

inline void AddEdge(int from, int to)
{
    edge[total].to = to;
    edge[total].next = head[from];
    head[from] = total++;
}

inline bool bfs()
{
    dis = INT_MAX;
    memset(disx, -1, sizeof(disx));
    memset(disy, -1, sizeof(disy));
    queue<int> que;
    for(int i = 0; i < n; i++){
        if(matchx[i] == -1){
            que.push(i);
            disx[i] = 0;
        }
    }
    while(!que.empty()){
        int u = que.front();
        que.pop();
        if( disx[u] > dis) break;
        for(int i = head[u]; i != -1; i = edge[i].next){
            int v = edge[i].to;
            if( disy[v] == -1){
                disy[v] = disx[u] + 1;
                if(matchy[v] == -1) dis = disy[v];
                else {
                    disx[matchy[v]] = disy[v] + 1;
                    que.push(matchy[v]);
                }
            }
        }
    }
    return dis != INT_MAX;
}

inline bool dfs(int u)
{
    for(int i = head[u]; i != -1; i = edge[i].next){
        int v = edge[i].to;
        if(!vis[v]){
            vis[v] = 1;
            if(matchy[v] != -1 && disy[v] == dis) continue;
            if(matchy[v] == -1 || dfs(matchy[v]) ){
                matchy[v] = u;
                matchx[u] = v;
                return true;
            }
        }   
    }
    return false;
}

inline int Hopcroft_Carp()
{
    int ans = 0;
    while( bfs() ){
        memset(vis, 0, sizeof(vis));
        for(int i = 0; i < n; i++){
            if(matchx[i] == -1 && dfs(i)) ans++;
        }
    }
    return ans;
}

int main()
{
    freopen("hdu2389.in","r",stdin);
    scanf("%d", &T);
    while(T-- > 0){
        init();
        scanf("%lf%d", &t, &n);
        for(int i = 0; i < n; i++){
            scanf("%lf%lf%lf",&x[i], &y[i], &v[i]);
        }
        scanf("%d",&m);
        for(int i = 0; i < m; i++){
            double tmpx, tmpy;
            scanf("%lf%lf",&tmpx, &tmpy);
            for(int j = 0; j < n; j++){
                double tmp = sqrt((tmpx - x[j]) * (tmpx - x[j]) + (tmpy - y[j]) * (tmpy - y[j]));
                if(v[j] * t >= tmp){
                    //printf("j = %d i = %d\n",j, i);
                    AddEdge(j,i);
                }
            }
        }
        int ans = Hopcroft_Carp();
        printf("Scenario #%d:\n%d\n\n",++cases,ans);
    }
    return 0;
}