Intervals—-最小費用流

題目：http://poj.org/problem?id=3680

還是建圖的問題。

離散化+最小費用流。

推薦博文：http://hi.baidu.com/juner_king/blog/item/a6b7cc822cba01dd9023d933.html

原始碼：(用時：547ms)

#include <stdio.h>#include <string.h>#include <algorithm>using namespace  std;typedef int typef;typedef int typec;const int N = 405, M = 2000;const typef inff = 0x3f3f3f3f;const typec infc = 0x3f3f3f3f;int a[N],b[N];int l[N],r[N],w[N];int x,n,k,cas;struct MinCostMaxFlow {int e, ev[M], nxt[M], head[N];typec cost[M], dist[N];typef cap[M];int pnt[N], road[N], q[N], bg, ed;bool vis[N];void init() { e = 0; memset(head,-1,sizeof(head)); }void addedge(int u, int v, typef f, typec c) { //u->v flow=f, cost=cev[e]=v; cap[e]=f; cost[e]=c; nxt[e]=head[u]; head[u]=e++;ev[e]=u; cap[e]=0; cost[e]=-c; nxt[e]=head[v]; head[v]=e++;}bool spfa(int s, int t, int n) {for(int i=0;i<=n;i++) dist[i] = infc, vis[i] = 0;bg = ed = dist[s] = 0;pnt[s] = s; q[ed++] = s;while (bg != ed) {int u = q[bg++]; vis[u] = 0;if (bg == N) bg = 0;for (int i = head[u]; ~i; i = nxt[i]) {if (cap[i] <= 0)continue;int v = ev[i];if (dist[v] > dist[u] + cost[i]) {dist[v] = dist[u] + cost[i];pnt[v] = u; road[v] = i;if (!vis[v]) {q[ed++] = v; vis[v] = 1;if(ed == N)ed = 0;}}}}return dist[t] != infc;}void mincost(int s, int t, int n, typef &f, typec &c) {c = f = 0;while(spfa(s, t, n)){typef minf = inff;for(int u = t; u != s; u = pnt[u])minf = min(minf, cap[road[u]]);for(int u = t; u != s; u = pnt[u]){cap[road[u]] -= minf;cap[road[u] ^ 1] += minf;}f += minf;c += minf * dist[t];}}};int solve(){    int xx,ll,rr;    int ans1,ans;    MinCostMaxFlow tmp;    sort(a,a+x);  xx=0;  b[xx++]=a[0];    for(int i=1;i<x;i++)      if(a[i]!=a[i-1])       b[xx++]=a[i];    tmp.init();    for(int i=1;i<=xx+1;i++)     tmp.addedge(i-1,i,k,0);   for(int i=1;i<=n;i++)    {        for(int j=0;j<xx;j++)          {              if(b[j]==l[i])               ll=j+1;              if(b[j]==r[i])               rr=j+1;          }       tmp.addedge(ll,rr,1,-w[i]);    }    tmp.mincost(0,xx+1,xx+2,ans1,ans);    return -ans;}int main(){    //freopen("F:\\a.txt","r",stdin);    scanf("%d",&cas);    while(cas--)    {        scanf("%d %d",&n,&k);        x=0;        for(int i=1;i<=n;i++)        {            scanf("%d %d %d",&l[i],&r[i],&w[i]);            a[x++]=l[i];  a[x++]=r[i];        }        printf("%d\n",solve());    }}