POJ 2112 Optimal Milking(最大流+二分)

题目链接

测试dinic模版，不知道这个模版到底对不对，那个题用这份dinic就是过不了。加上优化就WA，不加优化TLE。

#include <cstdio>
#include <string>
#include <cstring>
#include <queue>
#include <map>
#include <algorithm>
using namespace std;
#define INF 0x3ffffff
struct node
{
    int u,v,next,re,w;
} edge[200001];
int first[501],dis[501];
int p[251][251];
int t;
int sv,ev,K,C,M;
void CL()
{
    t = 1;
    memset(first,-1,sizeof(first));
}
void add(int u,int v,int w)
{
    edge[t].u = u;
    edge[t].v = v;
    edge[t].w = w;
    edge[t].re = t+1;
    edge[t].next = first[u];
    first[u] = t++;
    edge[t].u = v;
    edge[t].v = u;
    edge[t].w = 0;
    edge[t].re = t-1;
    edge[t].next = first[v];
    first[v] = t ++;
}
int bfs()
{
    int u,v,i;
    memset(dis,0xff,sizeof(dis));
    queue<int> que;
    que.push(sv);
    dis[sv] = 0;
    while(!que.empty())
    {
        u = que.front();
        que.pop();
        for(i = first[u]; i != -1; i = edge[i].next)
        {
            v = edge[i].v;
            if(edge[i].w > 0&&dis[v] < 0)
            {
                dis[v] = dis[u] + 1;
                que.push(v);
            }
        }
    }
    if(dis[ev] > 0) return 1;
    else return 0;
}
int dfs(int u,int step)
{
    int i,a = 0,v,flag = 0;
    if (u == ev) return step;
    for (i = first[u];i != -1&&flag < step; i = edge[i].next)//flag<step
    {
        v = edge[i].v;
        if (edge[i].w > 0&& dis[v] == dis[u]+1&&(a = dfs(v,min(step,edge[i].w))))
        {
            edge[i].w -= a;
            flag += a;//这里
            edge[edge[i].re].w += a;
            return a;
        }
    }
    if(flag == 0) dis[u] = -1;//这里
    return flag;
}
void build(int x)
{
    int i,j;
    CL();
    for(i = 1; i <= K; i ++)
    {
        add(0,i,M);
    }
    for(i = 1; i <= K; i ++)
    {
        for(j = 1; j <= C; j ++)
        {
            if(p[i][j+K] <= x)
            add(i,K+j,1);
        }
    }
    for(i = 1;i <= C;i ++)
    {
        add(i+K,ev,1);
    }
}
int fun(int x)
{
    int ans = 0,res;
    build(x);
    while(bfs())
    {
          while(res=dfs(sv,INF))
          ans += res;
    }
    if(ans == C)
        return 1;
    else
        return 0;
}
int bin(int l,int r)
{
    int str,mid,end;
    str = l;
    end = r;
    while(str < end)
    {
        mid = (str + end)/2;
        if(fun(mid))
        {
            end = mid;
        }
        else
        {
           str = mid + 1;
        }
    }
    return end;
}
int main()
{
    int i,j,k;
    while(scanf("%d%d%d",&K,&C,&M)!=EOF)
    {
        for(i = 1;i <= K+C;i ++)
        {
            for(j = 1;j <= K+C;j ++)
            {
                scanf("%d",&p[i][j]);
                if(i != j&&p[i][j] == 0)
                p[i][j] = INF;
            }
        }
        for(i = 1;i <= K+C;i ++)
        {
            for(j = 1;j <= K+C;j ++)
            {
                for(k = 1;k <= K+C;k ++)
                {
                    if(p[j][k] > p[j][i] + p[i][k])
                    p[j][k] = p[j][i] + p[i][k];
                }
            }
        }
        sv = 0;
        ev = K+C+1;
        int maxz = 0;
        for(i = 1;i <= K+C;i ++)
        {
            for(j = 1;j <= K+C;j ++)
            maxz = max(maxz,p[i][j]);
        }
        printf("%d
",bin(0,maxz));
    }
    return 0;
}