[有上下界的网络流]

有上下界的网络流请戳这里http://www.cnblogs.com/kane0526/archive/2013/04/05/3001108.html

转自hzwer.com

首先S向每天连[0,day]的边，每一天与拍照的妹子连[l,r]的边，每个女孩和汇连[g,oo]的边

对于有源和汇的上下界网络流，只要T到S连一条[0,inf]的边，那么原图成为一个无源点汇点的循环流图，那么新建SS和TT，向每个点连边（即每一点的入流为正则源向其连，否则向汇连），求SS到TT的最大流判断满流

判断有解之后求最大流再做一次S到T的最大流

同时要去掉原来T到S的[0,inf]的边

有下界的最小流QAQ
http://blog.youkuaiyun.com/popoqqq/article/details/48467349

其实我是来存代码的..=-=..

[BZOJ 2502]清理雪道

#include <bits/stdc++.h>
#define maxn 110
using namespace std;

int n;

const int inf = 0x7fffffff;

struct Edge{
    int to, next, w;
}edge[100010];

int h[maxn], cnt = 1;

void add(int u, int v, int w){
    cnt ++;edge[cnt].to = v;edge[cnt].next = h[u];
    edge[cnt].w = w;h[u] = cnt;
    swap(u, v), w = 0;
    cnt ++;edge[cnt].to = v;edge[cnt].next = h[u];
    edge[cnt].w = w;h[u] = cnt;
}

int S, T, SS, TT;

int ans;

void Restore(){
    for(int i = h[S]; i; i = edge[i].next)
        edge[i].w = edge[i^1].w = 0;
    for(int i = h[T]; i; i = edge[i].next)
        edge[i].w = edge[i^1].w = 0;
    for(int i = h[TT]; i; i = edge[i].next)
        if(edge[i].to == SS){
            ans = edge[i^1].w;
            edge[i].w = edge[i^1].w = 0;
            return;
        }
}

queue<int>Q;
int d[maxn];

bool BFS(){
    memset(d, -1, sizeof d);
    d[S] = 0;Q.push(S);
    while(!Q.empty()){
        int u = Q.front();Q.pop();
        for(int i = h[u]; i; i = edge[i].next){
            if(!edge[i].w)continue;
            int v = edge[i].to;
            if(d[v] == -1)d[v] = d[u] + 1, Q.push(v);
        }
    }
    return d[T] != -1;
}

int DFS(int x, int a){
    if(x == T || a == 0)return a;
    int used = 0, f;
    for(int i = h[x]; i; i = edge[i].next){
        int v = edge[i].to;
        if(d[v] == d[x] + 1 && edge[i].w){
            f = DFS(v, min(edge[i].w, a - used));
            edge[i].w -= f;
            edge[i^1].w += f;
            used += f;
            if(used == a)return used;
        }
    }
    if(!used)d[x] = -1;
    return used;
}

int Dinic(){
    int ans = 0;
    while(BFS())
        ans += DFS(S, inf);
    return ans;
}

int deg[maxn];

int main(){
    scanf("%d", &n);
    S = n+1, T = n+2, SS = n+3, TT = n+4;
    int x, m;
    for(int i = 1; i <= n; i ++){
        scanf("%d", &m);
        for(int j = 1; j <= m; j ++){
            scanf("%d", &x);
            add(i, x, inf);
            deg[i] --;
            deg[x] ++;
        }
    }

    for(int i = 1; i <= n; i ++){
        if(deg[i] > 0)add(S, i, deg[i]);
        else add(i, T, -deg[i]);
    }

    for(int i = 1; i <= n; i ++)
        add(SS, i, inf), add(i, TT, inf);
    add(TT, SS, inf);

    ans = Dinic();
    Restore();
    add(S, TT, inf);
    add(SS, T, inf);
    ans -= Dinic();
    cout << ans << endl;
    return 0;
}

[BZOJ 2055]80人环游世界

#include <bits/stdc++.h>
#define maxn 300
#define In(u) u
#define Out(u) u+n
using namespace std;
const int inf = 0x7ffffff;
int n, m;

int S, T, SS, TT;

struct Edge{
    int to, next, w, dis;
}edge[100010];

int h[maxn], cnt = 1;

void add(int u, int v, int w, int d){
    cnt ++;edge[cnt].to = v;edge[cnt].next = h[u];
    edge[cnt].w = w;edge[cnt].dis = d;h[u] = cnt;
    swap(u, v), w = 0, d = -d;
    cnt ++;edge[cnt].to = v;edge[cnt].next = h[u];
    edge[cnt].w = w;edge[cnt].dis = d;h[u] = cnt;
}

int ans;

queue<int>Q;
int dis[maxn], pre[maxn], vis[maxn];

bool Spfa(){
    memset(dis, 0x7f, sizeof dis);
    memset(vis, 0, sizeof vis);
    dis[S] = 0;Q.push(S);
    while(!Q.empty()){
        int u = Q.front(); Q.pop();
        for(int i = h[u]; i; i = edge[i].next){
            if(!edge[i].w)continue;
            int v = edge[i].to;
            if(dis[v] > dis[u] + edge[i].dis){
                pre[v] = i;
                dis[v] = dis[u] + edge[i].dis;
                if(!vis[v])vis[v] = true, Q.push(v);
            }
        }vis[u] = false;
    }
    return dis[T] < inf;
}

void End(){
    int ret = inf;
    for(int u = T, p; u != S; u = edge[p^1].to)
        p = pre[u], ret = min(ret, edge[p].w);
    ans += ret * dis[T];
    for(int u = T, p; u != S; u = edge[p^1].to){
        p = pre[u];
        edge[p].w -= ret;
        edge[p^1].w += ret;
    }
}

int solve(){
    while(Spfa())
        End();
    return ans;
}

int main(){
    scanf("%d%d", &n, &m);
    int x;
    S = 2 * n + 1, T = S + 1, SS = T + 1, TT = SS + 1;
    for(int i = 1; i <= n; i ++){
        scanf("%d", &x);
        add(S, In(i), x, 0);
        add(Out(i), T, x, 0);
        add(SS, Out(i), inf, 0);
        add(In(i), TT, inf, 0);
    }

    for(int i = 1; i <= n; i ++){
        for(int j = i+1; j <= n; j ++){
            scanf("%d", &x);
            if( ~x )add(In(i), Out(j), inf, x);
        }
    }

    add(TT, SS, m, 0);
    printf("%d\n", solve());
    return 0;
}