POJ 3680 最小费用最大流

建图如下

若限制为k

首先将坐标离散化。

对每个区间，左端点对应的编号到右端点对应的编号建一条边，容量为k，费用为负权

然后对每个编号i,建立i到i+1的边，容量为k，费用为0

起点和编号1连边，容量为k，费用0

最后一个编号和终点连边,容量为k，费用0

然后跑费用流即可

#include <iostream>#include <algorithm>#include <cstring>#include <string>#include <cstdio>#include <cmath>#include <queue>#include <map>#include <set>#define eps 1e-5#define MAXN 555#define MAXM 55555#define INF 100000007using namespace std;struct EDGE{    int v, cap, cost, next, re;    //  re记录逆边的下标。} edge[MAXM];int n, m, ans, flow, src, des;int e, head[MAXN];int que[MAXN], pre[MAXN], dis[MAXN];bool vis[MAXN];void init(){    e = ans = flow = 0;    memset(head, -1, sizeof(head));}void add(int u, int v, int cap, int cost){    edge[e].v = v;    edge[e].cap = cap;    edge[e].cost = cost;    edge[e].next = head[u];    edge[e].re = e + 1;    head[u] = e++;    edge[e].v = u;    edge[e].cap = 0;    edge[e].cost = -cost;    edge[e].next = head[v];    edge[e].re = e - 1;    head[v] = e++;}bool spfa(){    int i, h = 0, t = 1;    for(i = 0; i <= n; i ++)    {        dis[i] = INF;        vis[i] = false;    }    dis[src] = 0;    que[0] = src;    vis[src] = true;    while(t != h)    {        int u = que[h++];        h %= n;        vis[u] = false;        for(i = head[u]; i != -1; i = edge[i].next)        {            int v = edge[i].v;            if(edge[i].cap && dis[v] > dis[u] + edge[i].cost)            {                dis[v] = dis[u] + edge[i].cost;                pre[v] = i;                if(!vis[v])                {                    vis[v] = true;                    que[t++] = v;                    t %= n;                }            }        }    }    if(dis[des] == INF) return false;    return true;}void end(){    int u, p, mi = INF;    for(u = des; u != src; u = edge[edge[p].re].v)    {        p = pre[u];        mi = min(mi, edge[p].cap);    }    for(u = des; u != src; u = edge[edge[p].re].v)    {        p = pre[u];        edge[p].cap -= mi;        edge[edge[p].re].cap += mi;        ans += mi * edge[p].cost;     //  cost记录的为单位流量费用，必须得乘以流量。    }    flow += mi;}int nt, k;int a[MAXN], b[MAXN], w[MAXN];int x[MAXN];int bin(int low, int high, int v){    while(low <= high)    {        int mid = (low + high) >> 1;        if(x[mid] == v) return mid;        else if(x[mid] > v) high = mid - 1;        else low = mid + 1;    }    return -1;}void build(){    scanf("%d%d", &nt, &k);    int cnt = 0;    for(int i = 1; i <= nt; i++)    {        scanf("%d%d%d", &a[i], &b[i], &w[i]);        x[cnt++] = a[i];        x[cnt++] = b[i];    }    sort(x, x + cnt);    cnt = unique(x, x + cnt) - x;    for(int i = 1; i <= nt; i++)    {        int lx = bin(0, cnt - 1, a[i]) + 1;        int rx = bin(0, cnt - 1, b[i]) + 1;        add(lx, rx, 1, -w[i]);    }    for(int i = 1; i < cnt; i++)        add(i, i + 1, k, 0);    src = cnt + 1;    des = cnt + 2;    n = des;    add(src, 1, k, 0);    add(cnt, des, k, 0);}void MCMF(){    init();    build();    while(spfa()) end();}int main(){    int T;    scanf("%d", &T);    while(T--)    {        MCMF();        printf("%d\n", -ans);    }    return 0;}

zkw版   貌似比原作者写的指针版本的慢了不少，不过这种图zkw费用流本来就不擅长

#include <iostream>#include <algorithm>#include <cstring>#include <string>#include <cstdio>#include <cmath>#include <queue>#include <deque>#include <map>#include <set>#define eps 1e-5#define MAXN 5555#define MAXM 55555#define INF 100000007using namespace std;struct EDGE{    int cost, cap, v;    int next, re;}edge[MAXM];int head[MAXN], e;int vis[MAXN], d[MAXN];int ans, cost, src, des, n;void init(){    memset(head, -1, sizeof(head));    e = 0;    ans = cost = 0;}void add(int u, int v, int cap, int cost){    edge[e].v = v;    edge[e].cap = cap;    edge[e].cost = cost;    edge[e].re = e + 1;    edge[e].next = head[u];    head[u] = e++;    edge[e].v = u;    edge[e].cap = 0;    edge[e].cost = -cost;    edge[e].re = e - 1;    edge[e].next = head[v];    head[v] = e++;}int aug(int u, int f){    if(u == des)    {        ans += cost * f;        return f;    }    vis[u] = 1;    int tmp = f;    for(int i = head[u]; i != -1; i = edge[i].next)        if(edge[i].cap && !edge[i].cost && !vis[edge[i].v])        {            int delta = aug(edge[i].v, tmp < edge[i].cap ? tmp : edge[i].cap);            edge[i].cap -= delta;            edge[edge[i].re].cap += delta;            tmp -= delta;            if(!tmp) return f;        }    return f - tmp;}bool modlabel(){    for(int i = 0; i <= n; i++) d[i] = INF;    d[des] = 0;    deque<int>Q;    Q.push_back(des);    while(!Q.empty())    {        int u = Q.front(), tmp;        Q.pop_front();        for(int i = head[u]; i != -1; i = edge[i].next)            if(edge[edge[i].re].cap && (tmp = d[u] - edge[i].cost) < d[edge[i].v])                (d[edge[i].v] = tmp) <= d[Q.empty() ? src : Q.front()] ? Q.push_front(edge[i].v) : Q.push_back(edge[i].v);    }    for(int u = 1; u <= n; u++)        for(int i = head[u]; i != -1; i = edge[i].next)            edge[i].cost += d[edge[i].v] - d[u];    cost += d[src];    return d[src] < INF;}void costflow(){    while(modlabel())    {        do        {            memset(vis, 0, sizeof(vis));        }while(aug(src, INF));    }}int nt, k;int a[MAXN], b[MAXN], w[MAXN];int x[MAXN];int bin(int low, int high, int v){    while(low <= high)    {        int mid = (low + high) >> 1;        if(x[mid] == v) return mid;        else if(x[mid] > v) high = mid - 1;        else low = mid + 1;    }    return -1;}void build(){    scanf("%d%d", &nt, &k);    int cnt = 0;    for(int i = 1; i <= nt; i++)    {        scanf("%d%d%d", &a[i], &b[i], &w[i]);        x[cnt++] = a[i];        x[cnt++] = b[i];    }    sort(x, x + cnt);    cnt = unique(x, x + cnt) - x;    for(int i = 1; i <= nt; i++)    {        int lx = bin(0, cnt - 1, a[i]) + 1;        int rx = bin(0, cnt - 1, b[i]) + 1;        add(lx, rx, 1, -w[i]);    }    for(int i = 1; i < cnt; i++)        add(i, i + 1, k, 0);    src = cnt + 1;    des = cnt + 2;    n = des;    add(src, 1, k, 0);    add(cnt, des, k, 0);}int main(){    int T;    scanf("%d", &T);    while(T--)    {        init();        build();        costflow();        printf("%d\n", -ans);    }    return 0;}