hdu-4411-Arrest-费用流

#include<cstdio>
#include<cstring>
#include<iostream>
#include<cstdlib>
#include<algorithm>
using namespace std;

const int N = 1010;//点
const int M = 4 * 10010;//边
const int inf = 1000000000;
struct Node{//边，点f到点t，流量为c，费用为w
int f, t, c, w;
}e[M];
int next1[M], point
, dis
, q
, pre
, ne;//ne为已添加的边数，next，point为邻接表,dis为花费，pre为父亲节点
bool u
;
void init(){
memset(point, -1, sizeof(point));
ne = 0;
}
void add_edge(int f, int t, int d1, int d2, int w){//f到t的一条边，流量为d1,反向流量d2,花费w,反向边花费-w（可以反悔）
e[ne].f = f, e[ne].t = t, e[ne].c = d1, e[ne].w = w;
next1[ne] = point[f], point[f] = ne++;
e[ne].f = t, e[ne].t = f, e[ne].c = d2, e[ne].w = -w;
next1[ne] = point[t], point[t] = ne++;
}
bool spfa(int s, int t, int n){
int i, tmp, l, r;
memset(pre, -1, sizeof(pre));
for(i = 0; i < n; ++i)
dis[i] = inf;
dis[s] = 0;
q[0] = s;
l = 0, r = 1;
u[s] = true;
while(l != r) {
tmp = q[l];
l = (l + 1) % (n + 1);
u[tmp] = false;
for(i = point[tmp]; i != -1; i = next1[i]) {
if(e[i].c && dis[e[i].t] > dis[tmp] + e[i].w) {
dis[e[i].t] = dis[tmp] + e[i].w;
pre[e[i].t] = i;
if(!u[e[i].t]) {
u[e[i].t] = true;
q[r] = e[i].t;
r = (r + 1) % (n + 1);
}
}
}
}
if(pre[t] == -1)
return false;
return true;
}
void MCMF(int s, int t, int n, int &flow, int &cost){//起点s，终点t，点数n，最大流flow，最小花费cost
int tmp, arg;
flow = cost = 0;
while(spfa(s, t, n)) {
arg = inf, tmp = t;
while(tmp != s) {
arg = min(arg, e[pre[tmp]].c);
tmp = e[pre[tmp]].f;
}
tmp = t;
while(tmp != s) {
e[pre[tmp]].c -= arg;
e[pre[tmp] ^ 1].c += arg;
tmp = e[pre[tmp]].f;
}
flow += arg;
cost += arg * dis[t];
}
}
//建图前运行init()
//节点下标从0开始
//加边时运行add_edge(a,b,c,0,d)表示加一条a到b的流量为c花费为d的边（注意花费为单位流量花费）
//特别注意双向边，运行add_edge(a,b,c,0,d),add_edge(b,a,c,0,d)较好，不要只运行一次add_edge(a,b,c,c,d),费用会不对。
//求解时代入MCMF(s,t,n,v1,v2)，表示起点为s，终点为t，点数为n的图中，最大流为v1，最大花费为v2

int map[110][110];
int main()
{
int n,m,k,i,j,l;
while(cin>>n>>m>>k)
{
if(n==0&&m==0&&k==0) break;
for(i=0;i<=n;i++)
for(j=0;j<=n;j++)
if(i==j) map[i][j]=0;
else map[i][j]=inf;
while(m--)
{
int a,b,c;
cin>>a>>b>>c;
if(a!=b&&c<map[a][b])
map[a][b]=map[b][a]=c;
}
for(l=0;l<=n;l++)
for(i=0;i<=n;i++)
for(j=0;j<=n;j++)
map[i][j]=min(map[i][j],map[i][l]+map[l][j]);
init();
for(i=1;i<=n;i++){
add_edge(1,i+1,1,0,map[0][i]);
add_edge(i+1,i+1+n,1,0,-1000000);
for(j=1;j<i;j++)
add_edge(j+n+1,i+1,1,0,map[j][i]);
add_edge(i+n+1,2*n+2,1,0,map[0][i]);
}
add_edge(0,1,k,0,0);
add_edge(1,2*n+2,k,0,0);
int flow,cost;
MCMF(0,2*n+2,2*n+3,flow,cost);
int ans=cost+n*1000000;
cout<<ans<<endl;
}
}