【最大流之sap】【HDU1532】模板题

最新推荐文章于 2018-07-16 19:18:19 发布

zy691357966

最新推荐文章于 2018-07-16 19:18:19 发布

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本文链接：https://blog.youkuaiyun.com/zy691357966/article/details/44888195

本文详细解析了模板代码的功能和实现原理，通过实例展示了如何利用模板进行代码复用和优化，适用于初学者和有一定经验的开发者。

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与上题一样纯属测试模板

来自kuangbin的模板

#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <cstring>
#include <ctime>
#include <algorithm>
#include <iostream>
#include <sstream>
#include <string>
#define oo 0x13131313
using namespace std;
const int MAXN=200+5;
const int MAXM=2000;
const int INF=0x3f3f3f3f;
struct Edge
{
    int to,next,cap,flow;
    void get(int a,int b,int c,int d)
    {
        to=a;next=b;cap=c;flow=d;
    }
}edge[MAXM];
int tol;
int head[MAXN];
int gap[MAXN],dep[MAXN],pre[MAXN],cur[MAXN];
void init()
{
    tol=0;
    memset(head,-1,sizeof(head));
}
//单向图三个参数，无向图四个参数
void addedge(int u,int v,int w,int rw=0)
{
    edge[tol].get(v,head[u],w,0);head[u]=tol++;
    edge[tol].get(u,head[v],rw,0);head[v]=tol++;
}
int sap(int start,int end,int N)
{
    memset(gap,0,sizeof(gap));
    memset(dep,0,sizeof(dep));
    memcpy(cur,head,sizeof(head));
    int u=start;
    pre[u]=-1;
    gap[0]=N;
    int ans=0;
    while(dep[start]<N)
    {
        if(u==end)
        {
            int Min=INF;
            for(int i=pre[u];i!=-1;i=pre[edge[i^1].to])
                if(Min>edge[i].cap-edge[i].flow)
                   Min=edge[i].cap-edge[i].flow;
            for(int i=pre[u];i!=-1;i=pre[edge[i^1].to])
            {
                edge[i].flow+=Min;
                edge[i^1].flow-=Min;
            }
            u = start;
            ans+=Min;
            continue;
        }
        bool flag=false;
        int v;
        for(int i=cur[u];i !=-1;i=edge[i].next)
        {
            v=edge[i].to;
            if(edge[i].cap-edge[i].flow&&dep[v]+1==dep[u])
            {
                flag=true;
                cur[u]=pre[v]=i;
                break;
            }
        }
        if(flag)
        {
            u=v;
            continue;
        }
        int Min=N;
        for(int i=head[u];i!=-1;i=edge[i].next)
            if(edge[i].cap-edge[i].flow&&dep[edge[i].to]<Min)
        {
            Min=dep[edge[i].to];
            cur[u]=i;
        }
        gap[dep[u]]--;
        if(!gap[dep[u]]) return ans;
        dep[u]=Min+1;
        gap[dep[u]]++;
        if(u!=start) u=edge[pre[u]^1].to;
    }
    return ans;
}

完整代码：

#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <cstring>
#include <ctime>
#include <algorithm>
#include <iostream>
#include <sstream>
#include <string>
#define oo 0x13131313
using namespace std;
const int MAXN=200+5;
const int MAXM=2000;
const int INF=0x3f3f3f3f;
int n,m;
struct Edge
{
    int to,next,cap,flow;
    void get(int a,int b,int c,int d)
    {
        to=a;next=b;cap=c;flow=d;
    }
}edge[MAXM];
int tol;
int head[MAXN];
int gap[MAXN],dep[MAXN],pre[MAXN],cur[MAXN];
void init()
{
    tol=0;
    memset(head,-1,sizeof(head));
}
//单向图三个参数，无向图四个参数
void addedge(int u,int v,int w,int rw=0)
{
    edge[tol].get(v,head[u],w,0);head[u]=tol++;
    edge[tol].get(u,head[v],rw,0);head[v]=tol++;
}
int sap(int start,int end,int N)
{
    memset(gap,0,sizeof(gap));
    memset(dep,0,sizeof(dep));
    memcpy(cur,head,sizeof(head));
    int u=start;
    pre[u]=-1;
    gap[0]=N;
    int ans=0;
    while(dep[start]<N)
    {
        if(u==end)
        {
            int Min=INF;
            for(int i=pre[u];i!=-1;i=pre[edge[i^1].to])
                if(Min>edge[i].cap-edge[i].flow)
                   Min=edge[i].cap-edge[i].flow;
            for(int i=pre[u];i!=-1;i=pre[edge[i^1].to])
            {
                edge[i].flow+=Min;
                edge[i^1].flow-=Min;
            }
            u = start;
            ans+=Min;
            continue;
        }
        bool flag=false;
        int v;
        for(int i=cur[u];i !=-1;i=edge[i].next)
        {
            v=edge[i].to;
            if(edge[i].cap-edge[i].flow&&dep[v]+1==dep[u])
            {
                flag=true;
                cur[u]=pre[v]=i;
                break;
            }
        }
        if(flag)
        {
            u=v;
            continue;
        }
        int Min=N;
        for(int i=head[u];i!=-1;i=edge[i].next)
            if(edge[i].cap-edge[i].flow&&dep[edge[i].to]<Min)
        {
            Min=dep[edge[i].to];
            cur[u]=i;
        }
        gap[dep[u]]--;
        if(!gap[dep[u]]) return ans;
        dep[u]=Min+1;
        gap[dep[u]]++;
        if(u!=start) u=edge[pre[u]^1].to;
    }
    return ans;
}
void input()
{
    int a,b,c;
    for(int i=1;i<=m;i++)
    {
        scanf("%d%d%d",&a,&b,&c);
        addedge(a,b,c);
    }
}
void solve()
{
     int ANS=sap(1,n,n);
     printf("%d\n",ANS);
}
int main()
{
  //  freopen("a.in","r",stdin);
   // freopen("a.out","w",stdout);
    while(scanf("%d%d",&m,&n)!=EOF)
    {
        init();
        input();
        solve();
    }
    return 0;
}