hdu 1569 最大流

标签：blog   io   os   ar   for   sp   2014   on   log   

擦，搞了几个模板，都有错，就这个还好吧

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <algorithm>
#include <climits>
#include <vector>
#include <queue>
#include <cstdlib>
#include <string>
#include <set>
#include <stack>
#define LL long long
#define pii pair<int,int>
#define INF 0x3f3f3f3f
using namespace std;
const int maxn = 3000;
struct arc {
    int to,flow,next;
    arc(int x = 0,int y = 0,int z = 0) {
        to = x;
        flow = y;
        next = z;
    }
};
arc e[maxn*10];
int head[maxn],d[maxn],tot;
int S,T,q[maxn],hd,tail,n,m;
void add(int u,int v,int flow) {
    e[tot] = arc(v,flow,head[u]);
    head[u] = tot++;
    e[tot] = arc(u,0,head[v]);
    head[v] = tot++;
}
bool bfs() {
    for(int i = 1; i <= T; i++) d[i] = 0;
    d[S] = 1;
    hd = tail = 0;
    q[tail++] = S;
    while(hd < tail) {
        int u = q[hd++];
        for(int i = head[u]; ~i; i = e[i].next) {
            if(e[i].flow && !d[e[i].to]) {
                d[e[i].to] = d[u]+1;
                q[tail++] = e[i].to;
            }
        }
    }
    return d[T];
}
int dfs(int u,int low) {
    int tmp = 0,f;
    if(u == T || !low) return low;
    for(int i = head[u]; ~i; i = e[i].next) {
        if(d[e[i].to] == d[u]+1 && (f = dfs(e[i].to,min(low,e[i].flow)))) {
            tmp += f;
            e[i].flow -= f;
            e[i^1].flow += f;
            low -= f;
            if(!low) break;
        }
    }
    return tmp;
}
void init(){
    memset(head,-1,sizeof(head));
    tot = 0;
}
int main(){
   while(scanf("%d%d", &m,&n) != EOF)
    {
        init();
        int x;
        int sum = 0;
        S = 0;
        T = m * n + 1;
        for(int i = 1; i <= m; ++ i)
            for(int j = 1; j <= n; ++ j)
            {
                scanf("%d", &x);
                sum += x;
                if((i + j) & 1)
                {
                    add(S, (i - 1) * n + j, x);
                    //上
                    if(i > 1)  add((i - 1) * n + j, (i - 2) * n + j, INF);
                    //下
                    if(i < m)  add((i - 1) * n + j, i * n + j, INF);
                    //左
                    if(j > 1)  add((i - 1) * n + j, (i -1) * n + j - 1, INF);
                    //右
                    if(j < n)  add((i - 1) * n + j, (i - 1) * n + j + 1, INF);
                }
                else
                     add((i - 1) * n + j, T, x);
            }
            int ans = 0;
            while(bfs())ans+=dfs(S,INF);
            printf("%d\n",sum - ans);
    }
}

原来边就有权值的：

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <algorithm>
#include <climits>
#include <vector>
#include <queue>
#include <cstdlib>
#include <string>
#include <set>
#include <stack>
#define LL long long
#define pii pair<int,int>
#define INF 0x3f3f3f3f
using namespace std;
const int maxn = 3000;
struct arc {
    int to,cap,flow,next;
    arc(int x= 0 ,int y=0 ,int z=0 ,int u=0) {
        to = x;
        cap = y;
        flow = z;
        next = u;
    }
};
arc e[maxn*10];
int head[maxn],d[maxn],tot;
int S,T,q[maxn],hd,tail,n,m;
void add(int u,int v,int cap,int flow) {
    e[tot] = arc(v,cap,flow,head[u]);
    head[u] = tot++;
    e[tot] = arc(u,0,-flow,head[v]);
    head[v] = tot++;
}
bool bfs() {
    for(int i = 1; i <= T; i++) d[i] = 0;
    d[S] = 1;
    hd = tail = 0;
    q[tail++] = S;
    while(hd < tail) {
        int u = q[hd++];
        for(int i = head[u]; ~i; i = e[i].next) {
            if(e[i].cap > e[i].flow && !d[e[i].to]) {
                d[e[i].to] = d[u]+1;
                q[tail++] = e[i].to;
            }
        }
    }
    return d[T];
}
int dfs(int u,int low) {
    int tmp = 0,f;
    if(u == T || !low) return low;
    for(int i = head[u]; ~i; i = e[i].next) {
        if(d[e[i].to] == d[u]+1 && (f = dfs(e[i].to,min(low,e[i].cap-e[i].flow)))) {
            tmp += f;
            e[i].flow += f;
            e[i^1].flow -= f;
            low -= f;
            if(!low) break;
        }
    }
    return tmp;
}
void init(){
    memset(head,-1,sizeof(head));
    tot = 0;
}
int main(){
   while(scanf("%d%d", &m,&n) != EOF)
    {
        init();
        int x;
        int sum = 0;
        S = 0;
        T = m * n + 1;
        for(int i = 1; i <= m; ++ i)
            for(int j = 1; j <= n; ++ j)
            {
                scanf("%d", &x);
                sum += x;
                if((i + j) & 1)
                {
                    add(S, (i - 1) * n + j, x,0);
                    //上
                    if(i > 1)  add((i - 1) * n + j, (i - 2) * n + j, INF,0);
                    //下
                    if(i < m)  add((i - 1) * n + j, i * n + j, INF,0);
                    //左
                    if(j > 1)  add((i - 1) * n + j, (i -1) * n + j - 1, INF,0);
                    //右
                    if(j < n)  add((i - 1) * n + j, (i - 1) * n + j + 1, INF,0);
                }
                else
                     add((i - 1) * n + j, T, x,0);
            }
            int ans = 0;
            while(bfs())ans+=dfs(S,INF);
            printf("%d\n",sum - ans);
    }
}

hdu 1569 最大流

标签：blog   io   os   ar   for   sp   2014   on   log   

原文地址：http://blog.csdn.net/wyl_zheyang/article/details/40072647