HDU 3987 最小割模型

读完题后，就知道是最小割了，最小割=最大流，但是题目又说要最少边的最小割，输出边的个数

这样建边得时候就要换种方式了，将边权w变为w *(E + 1) + 1，这时候求出的最大流实际上附带了一个信息，就是边的个数，最后的结果直接mod （E+1 ）即可

/*
ID: CUGB-wwj
PROG:
LANG: C++
*/
#include <iostream>
#include <vector>
#include <list>
#include <map>
#include <set>
#include <deque>
#include <queue>
#include <stack>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cctype>
#include <string>
#include <cstring>
#include <cmath>
#include <ctime>
#define INF 11111111111111LL
#define MAXN 1005
#define MAXM 444444
#define PI acos(-1.0)
using namespace std;
struct node
{
int ver;    // vertex
long long cap;    // capacity
long long flow;   // current flow in this arc
int next, rev;
}edge[MAXM];
long long dist[MAXN];
int numbs[MAXN], src, des, n, m;
int head[MAXN], e;
void add(int x, int y, long long  c)
{       //e记录边的总数
edge[e].ver = y;
edge[e].cap = c;
edge[e].flow = 0;
edge[e].rev = e + 1;        //反向边在edge中的下标位置
edge[e].next = head[x];   //记录以x为起点的上一条边在edge中的下标位置
head[x] = e++;           //以x为起点的边的位置
//反向边
edge[e].ver = x;
edge[e].cap = 0;  //反向边的初始网络流为0
edge[e].flow = 0;
edge[e].rev = e - 1;
edge[e].next = head[y];
head[y] = e++;
}
void rev_BFS()
{
int Q[MAXN], qhead = 0, qtail = 0;
for(int i = 1; i <= n; ++i)
{
dist[i] = MAXN;
numbs[i] = 0;
}
Q[qtail++] = des;
dist[des] = 0;
numbs[0] = 1;
while(qhead != qtail)
{
int v = Q[qhead++];
for(int i = head[v]; i != -1; i = edge[i].next)
{
if(edge[edge[i].rev].cap == 0 || dist[edge[i].ver] < MAXN)continue;
dist[edge[i].ver] = dist[v] + 1;
++numbs[dist[edge[i].ver]];
Q[qtail++] = edge[i].ver;
}
}
}

long long  maxflow()
{
int u;
long long totalflow = 0;
int Curhead[MAXN], revpath[MAXN];
for(int i = 1; i <= n; ++i)Curhead[i] = head[i];
u = src;
while(dist[src] < n)
{
if(u == des)     // find an augmenting path
{
long long  augflow = INF;
for(int i = src; i != des; i = edge[Curhead[i]].ver)
augflow = min(augflow, edge[Curhead[i]].cap);
for(int i = src; i != des; i = edge[Curhead[i]].ver)
{
edge[Curhead[i]].cap -= augflow;
edge[edge[Curhead[i]].rev].cap += augflow;
edge[Curhead[i]].flow += augflow;
edge[edge[Curhead[i]].rev].flow -= augflow;
}
totalflow += augflow;
u = src;
}
int i;
for(i = Curhead[u]; i != -1; i = edge[i].next)
if(edge[i].cap > 0 && dist[u] == dist[edge[i].ver] + 1)break;
if(i != -1)     // find an admissible arc, then Advance
{
Curhead[u] = i;
revpath[edge[i].ver] = edge[i].rev;
u = edge[i].ver;
}
else        // no admissible arc, then relabel this vertex
{
if(0 == (--numbs[dist[u]]))break;    // GAP cut, Important!
Curhead[u] = head[u];
long long  mindist = n;
for(int j = head[u]; j != -1; j = edge[j].next)
if(edge[j].cap > 0)mindist = min(mindist, dist[edge[j].ver]);
dist[u] = mindist + 1;
++numbs[dist[u]];
if(u != src)
u = edge[revpath[u]].ver;    // Backtrack
}
}
return totalflow;
}
void init()
{
e = 0;
memset(head, -1, sizeof(head));
}
int main()
{
int T;
scanf("%d", &T);
int x, y, fg;
long long z;
int cas = 0;
while(T--)
{
init();
scanf("%d%d", &n, &m);
for(int i = 0; i < m; i++)
{
scanf("%d%d%I64d%d", &x, &y, &z, &fg);
add(x + 1, y + 1, z * 222222LL + 1);
if(fg) add(y + 1, x + 1, z * 222222LL + 1);
}
src = 1;
des = n;
rev_BFS();
long long  ans = maxflow() % 222222LL;
printf("Case %d: %I64d\n", ++cas, ans);
}
return 0;
}