hdu_4280

2012 icpc 长春赛区的最大流模板题, 模板的高效性很重要

#include <cstdio>
#include <cstring>
#include <queue>
#include <algorithm>
#define MAXVERTEX	100001
#define MAXARC 		400010
#define INF			0x7fffffff
#pragma comment(linker, "/STACK:1024000000,1024000000")
using namespace std; 

struct Edge{
	int v, val, next;
}edge[MAXARC];

int vertex, e_gap, head[MAXVERTEX];
int pre[MAXVERTEX], cur[MAXVERTEX], dis[MAXVERTEX], gap[MAXVERTEX];

void insert_arc(int u, int v, int w)
{
	edge[e_gap].v = v;	edge[e_gap].val = w;
	edge[e_gap].next = head[u];	head[u] = e_gap ++;
	swap(u, v);
	edge[e_gap].v = v;	edge[e_gap].val = 0;
	edge[e_gap].next = head[u];	head[u] = e_gap ++;
}

void bfs(int source, int sink)
{
	int u, v;
	queue<int> q;
	memset(dis, -1, sizeof(dis));
	memset(gap, 0, sizeof(gap));
	dis[sink] = 0;
	gap[0] = 1;	q.push(sink);

	while( !q.empty() ) {
		u = q.front(); q.pop();
		for(int i = head[u]; -1 != i; i = edge[i].next) {
			v = edge[i].v;
			if( edge[i].val || -1 != dis[v] )	continue;
			dis[v] = dis[u]+1;	gap[ dis[v] ] ++;
			q.push(v);
		}
	}
}

int i_sap(int source, int sink)
{
	int u(source), v, min_dis, max_flow(0), path_flow(INF);
	bfs(source, sink);

	for(int i = 0; i <= vertex; i ++)
		cur[i] = head[i];

	gap[0] = vertex; pre[u] = u;
	while( dis[source] < vertex ) {
loop:
		for(int &i = cur[u]; -1 != i; i = edge[i].next) {
			v = edge[i].v;
			if( !edge[i].val || (dis[u] != dis[v]+1) )	continue;
			pre[v] = u;	path_flow = min(path_flow, edge[i].val);
			u = v;
			if( v == sink ) {
				for(u = pre[u]; v != source; v = u, u = pre[u]) {
					edge[cur[u]].val -= path_flow;	edge[cur[u]^1].val += path_flow;
				}
				max_flow += path_flow; path_flow = INF;
			}
			goto loop;
		}
		min_dis = vertex;
		for(int i = head[u]; -1 != i; i = edge[i].next) {
			v = edge[i].v;
			if( edge[i].val && min_dis > dis[v] ) {
				cur[u] = i; min_dis = dis[v];
			}
		}
		gap[ dis[u] ] --;
		if( !gap[ dis[u] ] )	break;
		dis[u] = min_dis+1;
		gap[ dis[u] ] ++;	u = pre[u];
	}
	return max_flow;
}

int main(int argc, char const *argv[])
{
	//freopen("test.in", "r", stdin);
	int cas, arc, source, sink, x, y, v, max_x, min_x;
	scanf("%d", &cas);
	while( cas-- ) {
		scanf("%d %d", &vertex, &arc);
		max_x = -INF; min_x = INF;
		for(int i = 1; i <= vertex; i ++) {
			scanf("%d %d", &x, &y);
			if( min_x > x ) {
				min_x = x;	source = i;
			}
			if( max_x < x ) {
				max_x = x; 	sink = i;
			}
		}

		e_gap = 0;
		memset(head, -1, sizeof(head));
		for(int i = 0; i < arc; i ++) {
			scanf("%d %d %d", &x, &y, &v);
			insert_arc(x, y, v);	insert_arc(y, x, v);
		}
		printf("%d\n", i_sap(source, sink));
	}
	return 0;
}