图论——最大流（DINIC）

Posted 2020-08-04 HITLJR

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
#define INF 0x3f3f3f3f
using namespace std;
int dis[300];//BFS深度int q[30000],h,r;//BFS队列
int e;//终点
int head[300];//邻接表头指针
int current[300];//当前弧优化struct edge
{
    int to,v;
    int next;
}E[333333];
int tot;
void addedge(int a,int b,int v)
{
    E[tot].to = b;
    E[tot].v = v;
    E[tot].next = head[a];
    head[a] = tot++;
    E[tot].to = a;
    E[tot].v = 0;
    E[tot].next = head[b];
    head[b] = tot++;
}
void init()
{
    memset(E,0,sizeof(E));
    memset(head,-1,sizeof(head));
    tot = 0;
}
int BFS(int b)
{
    int u;
    memset(dis,-1,sizeof(dis));
    dis[b] = 0;
    h = 0; r=1;
    q[1] = b;
    while(h < r)
    {
        u = q[++h];
        for (int i = head[u]; i!=-1;i = E[i].next)
        {
            int v = E[i].to;
            if (dis[v] < 0&&E[i].v > 0)
            {
                dis[v] = dis[u]+1;
                q[++r] = v;
            }
        }
    }
    if (dis[e]>0) return 1;
    else return 0;
}
int dinic(int x ,int low)
{
    int i,a = 0;
    if (x==e) return low;
    for (i = current[x]; i !=-1 ; i = E[i].next)
    {
        current[x] = i;
        int v = E[i].to;
        if (E[i].v > 0&&dis[v]==dis[x]+1 && (a=dinic(v,min(low,E[i].v))))
        {
            E[i].v -= a;
            E[i^1].v += a;
            return a;
        }
    }
    return 0;
}
int main()
{   
    int t;int ANS;
    init();
    int b = ?//起点main局部变量
    e = ?//全局变量
    int tans;
    while(BFS(b))
       {
          for (int i = 0; i<=e;i++)
          current[i] = head[i];
          while (tans = dinic(b,0x3f3f3f3f)) ANS+=tans;
       }
    cout << ANS <<endl;
    return 0;
}