poj 2112 Optimal Milking

#define _CRT_SECURE_NO_DEPRECATE
#include<iostream>
#include<algorithm>
#include<queue>
#include<set>
#include<vector>
#include<cstring>
#include<string>
using namespace std;
#define INF 0x3f3f3f3f
const int K_MAX = 30+2, C_MAX = 200+2, V_MAX = K_MAX+C_MAX + 2;
typedef long long ll;
int V;
struct edge {
    int to, cap, rev;
    edge(int to, int cap, int rev) :to(to), cap(cap), rev(rev) {}
};
vector<edge>G[V_MAX];
int level[V_MAX];
int iter[V_MAX];

void add_edge(int from, int to, int cap) {
    G[from].push_back(edge(to, cap, G[to].size()));
    G[to].push_back(edge(from, 0, G[from].size() - 1));
}

void bfs(int s) {
    memset(level, -1, sizeof(level));
    queue<int>que;
    level[s] = 0;
    que.push(s);
    while (!que.empty()) {
        int v = que.front(); que.pop();
        for (int i = 0; i < G[v].size(); i++) {
            edge&e = G[v][i];
            if (e.cap > 0 && level[e.to] < 0) {
                level[e.to] = level[v] + 1;
                que.push(e.to);
            }
        }
    }
}

int dfs(int v, int t, int f) {
    if (v == t)return f;
    for (int &i = iter[v]; i < G[v].size(); i++) {
        edge&e = G[v][i];
        if (e.cap > 0 && level[v] < level[e.to]) {
            int d = dfs(e.to, t, min(f, e.cap));
            if (d > 0) {
                e.cap -= d;
                G[e.to][e.rev].cap += d;
                return d;
            }
        }
    }
    return 0;
}

int max_flow(int s, int t) {
    int flow = 0;
    for (;;) {
        bfs(s);
        if (level[t] < 0)return flow;
        memset(iter, 0, sizeof(iter));
        int f;
        while ((f = dfs(s, t, INT_MAX))>0) {
            flow += f;
        }
    }
}

int k, c, m,s,t;
int d[K_MAX+C_MAX][K_MAX+C_MAX];

void floyd() {
    for (int K = 0; K < k + c; K++)
        for (int i = 0; i < k + c; i++)
            for (int j = 0; j < k + c; j++)
                d[i][j] = min(d[i][j],d[i][K]+d[K][j]);
}

bool C(int limit) {
    for (int i = 0; i < V;i++) {
        G[i].clear();
    }
    for (int i = 0; i < c;i++) {
        add_edge(s,i,1);
    }
    for (int i = 0; i < k;i++) {
        add_edge(c+i,t,m);
    }
    for (int i = 0; i < c;i++) {//牛与机器连边,i:牛
        for (int j = 0; j < k;j++) {//j:机器
            if (d[j][k+i] <= limit)
                add_edge(i, c + j, 1);
        }
    }

    return max_flow(s,t)==c;//如果最大流等于牛的个数

}

int main() {
    while (scanf("%d%d%d", &k, &c, &m) != EOF) {
        for (int i = 0; i < k + c; i++)
            for (int j = 0; j < k + c; j++) {
                scanf("%d", &d[i][j]);
                if (!d[i][j])d[i][j] = INF;//!!Entities not directly connected by a path have a distance of 0
            }
        floyd();
        //0~c-1:牛
        //c~c+k-1:挤奶机
        s = k + c, t = s+1,V=t+1;

        int lb = 0, ub = 200 * (k + c);
        while (ub - lb > 1) {
            int mid = (lb+ub) >> 1;
            if (C(mid))ub = mid;
            else lb = mid;
        }
        printf("%d\n",ub);
    }
    return 0;
}