POJ 2289 Jamie's Contact Groups(二分+最大流)

版权声明：get busy living...or get busy dying https://blog.csdn.net/qq_41444888/article/details/89319367

http://poj.org/problem?id=2289

二分流入汇点的流量，保证最小化最大值，但是二分真是个很严重的问题，哎

直接把两个AC代码挂上吧，硬刚是刚不过了，会用就行了。。

#include<iostream>
#include<cstring>
#include<cstdio>
#include<algorithm>
#include<vector>
#include<set>
#include<map>
#include<queue>
#include<cmath>
#define ll long long
#define mod 1000000007
#define inf 0x3f3f3f3f
using namespace std;
const int maxn = 50005;
int cnt, st, en;
int n, m;
int u, v, w;
struct node
{
    int to, next, w;
}e[2000005];
int head[maxn], depth[maxn], cur[maxn];
void init()
{
    st = 0, en = n + m + 1;
    cnt = 0;
    memset(head, -1, sizeof(head));
}
void addedge(int u, int v, int w)
{
    e[cnt].w = w;
    e[cnt].to = v;
    e[cnt].next = head[u];
    head[u] = cnt ++;

    e[cnt].w = 0;
    e[cnt].to = u;
    e[cnt].next = head[v];
    head[v] = cnt ++;
}
int dfs(int u, int flow)
{
    if(u == en) return flow;
    for(int& i = cur[u]; ~i; i = e[i].next)
    {
        if(depth[e[i].to] == depth[u] + 1 && (e[i].w != 0))
        {
            int zen = dfs(e[i].to, min(e[i].w, flow));
            if(zen)
            {
                e[i].w -= zen;
                e[i^1].w += zen;
                return zen;
            }
        }
    }
    return 0;
}
int bfs()
{
    queue<int> q;
    while(! q.empty()) q.pop();
    memset(depth, 0, sizeof(depth));
    depth[st] = 1;
    q.push(st);
    while(! q.empty())
    {
        int h = q.front();
        q.pop();
        for(int i = head[h]; ~i; i = e[i].next)
        {
            if((! depth[e[i].to]) && e[i].w)
            {
                depth[e[i].to] = depth[h] + 1;
                q.push(e[i].to);
            }
        }
    }
    if(depth[en]) return 1;
    return 0;
}
int dinic()
{
    int ans = 0;
    while(bfs())
    {
        for(int i = 0; i <= n + m + 1; i ++)
            cur[i] = head[i];
        while(int d = dfs(st, inf))
            ans += d;
    }
    return ans;
}
char tmp[20];
int tmp1;
vector<int> V[maxn];
int main()
{
    while(scanf("%d%d", &n, &m) != EOF && (n + m))
    {
        for(int i = 1; i <= n; i ++)
        {
            V[i].clear();
            scanf("%s", tmp);
            while(getchar() != '\n')
            {
                scanf("%d", &tmp1);
                V[i].push_back(tmp1+1);
            }
        }
        int l = 1, r = n, mid;
        //int ans = 0;
        while(l < r)
        {
            init();
            mid = (l + r) / 2;
            for(int i = 1; i <= n; i ++)
                addedge(0, i, 1);
            for(int i = 1; i <= m; i ++)
                addedge(i + n, n + m + 1, mid);
            for(int i = 1; i <= n; i ++)
                for(int j = 0; j < V[i].size(); j ++)
                    addedge(i, V[i][j] + n, 1);
            if(dinic() == n)
            {
                r = mid;
            }
            else l = mid + 1;
        }
        printf("%d\n", l);
    }
    return 0;
}

#include<iostream>
#include<cstring>
#include<cstdio>
#include<algorithm>
#include<vector>
#include<set>
#include<map>
#include<queue>
#include<cmath>
#define ll long long
#define mod 1000000007
#define inf 0x3f3f3f3f
using namespace std;
const int maxn = 50005;
int cnt, st, en;
int n, m;
int u, v, w;
struct node
{
    int to, next, w;
}e[2000005];
int head[maxn], depth[maxn], cur[maxn];
void init()
{
    st = 0, en = n + m + 1;
    cnt = 0;
    memset(head, -1, sizeof(head));
}
void addedge(int u, int v, int w)
{
    e[cnt].w = w;
    e[cnt].to = v;
    e[cnt].next = head[u];
    head[u] = cnt ++;

    e[cnt].w = 0;
    e[cnt].to = u;
    e[cnt].next = head[v];
    head[v] = cnt ++;
}
int dfs(int u, int flow)
{
    if(u == en) return flow;
    for(int& i = cur[u]; ~i; i = e[i].next)
    {
        if(depth[e[i].to] == depth[u] + 1 && (e[i].w != 0))
        {
            int zen = dfs(e[i].to, min(e[i].w, flow));
            if(zen)
            {
                e[i].w -= zen;
                e[i^1].w += zen;
                return zen;
            }
        }
    }
    return 0;
}
int bfs()
{
    queue<int> q;
    while(! q.empty()) q.pop();
    memset(depth, 0, sizeof(depth));
    depth[st] = 1;
    q.push(st);
    while(! q.empty())
    {
        int h = q.front();
        q.pop();
        for(int i = head[h]; ~i; i = e[i].next)
        {
            if((! depth[e[i].to]) && e[i].w)
            {
                depth[e[i].to] = depth[h] + 1;
                q.push(e[i].to);
            }
        }
    }
    if(depth[en]) return 1;
    return 0;
}
int dinic()
{
    int ans = 0;
    while(bfs())
    {
        for(int i = 0; i <= n + m + 1; i ++)
            cur[i] = head[i];
        while(int d = dfs(st, inf))
            ans += d;
    }
    return ans;
}
char tmp[20];
int tmp1;
vector<int> V[maxn];
int main()
{
    while(scanf("%d%d", &n, &m) != EOF && (n + m))
    {
        for(int i = 1; i <= n; i ++)
        {
            V[i].clear();
            scanf("%s", tmp);
            while(getchar() != '\n')
            {
                scanf("%d", &tmp1);
                V[i].push_back(tmp1+1);
            }
        }
        int l = 1, r = n, mid;
        int ans = 0;
        while(l <= r)
        {
            init();
            mid = (l + r) / 2;
            for(int i = 1; i <= n; i ++)
                addedge(0, i, 1);
            for(int i = 1; i <= m; i ++)
                addedge(i + n, n + m + 1, mid);
            for(int i = 1; i <= n; i ++)
                for(int j = 0; j < V[i].size(); j ++)
                    addedge(i, V[i][j] + n, 1);
            if(dinic() == n)
            {
                ans = mid;
                r = mid - 1;
            }
            else l = mid + 1;
        }
        printf("%d\n", ans);
    }
    return 0;
}