Secret Milking Machine

#include<iostream>
#include<string.h>

#include<stdio.h>
#define VM 4005
#define INF  0x3f3f3f3f
using namespace std;
int n,m;
int s,sink;
int head[VM],dep[VM],gap[VM];
struct node
{
int frm;
int to;
int cap;
int next;
}edge[999999];

struct node1
{
int u;
int v;
int c;
}p[999999];

int tot;
int tmpn;
void add(int u, int v, int c)
{
edge[tot].frm = u;
edge[tot].to = v;
edge[tot].cap = c;
edge[tot].next = head[u];
head[u] = tot++;
edge[tot].frm = v;
edge[tot].to = u;
edge[tot].cap = 0;
edge[tot].next = head[v];
head[v] = tot++;
}
void BFS(int src, int des)
{
memset(dep, -1, sizeof(dep));
memset(gap, 0, sizeof(gap));
gap[0] = 1;   //说明此时有1个dep[i] = 0
int Q[VM], front = 0, rear = 0;
dep[des] = 0;
Q[rear++] = des;
int u, v;
while (front != rear)
{
u = Q[front++];
front = front%VM;
for (int i=head[u]; i!=-1; i=edge[i].next)
{
v = edge[i].to;
if (edge[i].cap != 0 || dep[v] != -1)
continue;
Q[rear++] = v;
rear = rear % VM;
++gap[dep[v] = dep[u] + 1];  //求出各层次的数量
}
}
}
int SAP(int src, int des)
{
int res = 0;
BFS(src, des);
int cur[VM];
int S[VM], top = 0;
memcpy(cur, head, sizeof(head));
int u = src, i;

while (dep[src] < n)   //n为结点的个数
{
if (u == des)
{
int temp = INF, inser = n;
for (i=0; i!=top; ++i)
if (temp > edge[S[i]].cap)
{
temp = edge[S[i]].cap;
inser = i;
}
for (i=0; i!=top; ++i)
{
edge[S[i]].cap -= temp;
edge[S[i]^1].cap += temp;
}
res += temp;
top = inser;
u = edge[S[top]].frm;
}

if (u != des && gap[dep[u] -1] == 0)//出现断层，无增广路
break;
for (i = cur[u]; i != -1; i = edge[i].next)//遍历与u相连的未遍历结点
if (edge[i].cap != 0 && dep[u] == dep[edge[i].to] + 1) //层序关系， 找到允许
break;

if (i != -1)//找到允许弧
{
cur[u] = i;
S[top++] = i;//加入路径栈
u = edge[i].to;//查找下一个结点
}
else   //无允许的路径，修改标号当前点的标号比与之相连的点中最小的多1
{
int min = n;
for (i = head[u]; i != -1; i = edge[i].next) //找到与u相连的v中dep[v]最小的点
{
if (edge[i].cap == 0)
continue;
if (min > dep[edge[i].to])
{
min = dep[edge[i].to];
cur[u] = i;          //最小标号就是最新的允许弧
}
}
--gap[dep[u]];          //dep[u] 的个数变化了 所以修改gap
++gap[dep[u] = min + 1]; //将dep[u]设为min(dep[v]) + 1, 同时修改相应的gap[]
if (u != src) //该点非源点&&以u开始的允许弧不存在，退点
u = edge[S[--top]].frm;
}
}

return res;
}

int isBuild(int mid,int tt)
{
memset(head,-1,sizeof(head));
tot=0;
add(s,1,tt);
for(int i=0;i<m;i++)
{
if(p[i].c<=mid)//小于中间流量的建边
{
add(p[i].u,p[i].v,1);
add(p[i].v,p[i].u,1);
}
}
add(tmpn,sink,tt);
if(SAP(s,sink)>=tt)
return 1;
return 0;
}
int main()
{
int minc,maxc;
int t;
while(scanf("%d%d%d",&n,&m,&t)!=EOF)
{
minc=99999999;
maxc=0;
tmpn=n;
s=0;
sink=n+1;
n+=2;
for(int i=0;i<m;i++)
{
scanf("%d%d%d",&p[i].u,&p[i].v,&p[i].c);
if(minc>p[i].c)
minc=p[i].c;
if(maxc<p[i].c)
maxc=p[i].c;
}
int ans=0;
while(minc<=maxc)//二分
{
int mid=(maxc+minc)>>1;
if(isBuild(mid,t))
{
maxc=mid-1;
ans=mid;
}
else
minc=mid+1;
}
printf("%d\n",ans);
}
return 0;
}

#include<iostream>
#include<string.h>

#include<stdio.h>
#define VM 4005
#define INF  0x3f3f3f3f
using namespace std;
int n,m;
int s,sink;
int head[VM],dist[VM],gap[VM],cur[VM],pre[VM];
struct node
{
int to;
int cap;
int nxt;
}edge[999999];

struct node1
{
int u;
int v;
int c;
}p[999999];

int ep;
int tmpn;

void add(int cu,int cv,int cw)
{

edge[ep].to = cv;
edge[ep].cap = cw;
edge[ep].nxt = head[cu];
head[cu] = ep;
ep ++;
edge[ep].to = cu;
edge[ep].cap = 0;
edge[ep].nxt = head[cv];
head[cv] = ep;
ep ++;
}
int min (int a ,int b)
{
return a > b ? b : a;
}

int sap (int src,int des,int n)
{
memset (dist,0,sizeof(dist));
memset (gap,0,sizeof (dist));
memcpy (cur,head,sizeof(dist));
int res = 0;
int u = pre[src] = src;
int aug = INF;
gap[0] = n;
while (dist[src] < n)
{
loop:
for (int &i = cur[u];i != -1;i = edge[i].nxt)
{
int v = edge[i].to;
if (edge[i].cap && dist[u] == dist[v] + 1)
{
aug = min (aug,edge[i].cap);
pre[v] = u;
u = v;
if (v == des)
{
res += aug;
for (u = pre[u];v != src;v = u,u = pre[u])
{
edge[cur[u]].cap -= aug;
edge[cur[u]^1].cap += aug;
}
aug = INF; //
}
goto loop;
}
}
int mindist = n;  //
for (int i = head[u];i != -1;i = edge[i].nxt)
{
int v = edge[i].to;
if (edge[i].cap && mindist > dist[v])
{
cur[u] = i;
mindist = dist[v];
}
}
if ((--gap[dist[u]]) == 0)
break;
dist[u] = mindist + 1;
gap[dist[u]] ++;
u = pre[u];
}
return res;
}

int isBuild(int mid,int tt)
{
memset(head,-1,sizeof(head));
ep=0;
add(s,1,tt);
for(int i=0;i<m;i++)
{
if(p[i].c<=mid)
{
add(p[i].u,p[i].v,1);
add(p[i].v,p[i].u,1);
}
}
add(tmpn,sink,tt);
if(sap(s,sink,n)>=tt)
return 1;
return 0;
}
int main()
{
int minc,maxc;
int t;
while(scanf("%d%d%d",&n,&m,&t)!=EOF)
{
minc=99999999;
maxc=0;
tmpn=n;
s=0;
sink=n+1;
n+=2;
for(int i=0;i<m;i++)
{
scanf("%d%d%d",&p[i].u,&p[i].v,&p[i].c);
if(minc>p[i].c)
minc=p[i].c;
if(maxc<p[i].c)
maxc=p[i].c;
}
int ans=0;
while(minc<=maxc)
{
int mid=(maxc+minc)>>1;
if(isBuild(mid,t))
{
maxc=mid-1;
ans=mid;
}
else
minc=mid+1;
}
printf("%d\n",ans);
}
return 0;
}