HDU 4280 Island Transport（dinic弧优化+双向图建边）

• 直接跑dinic会t
• 需要弧优化
• 然后双向边不需要建立反向弧，直接正反建边即可

#include<algorithm>
#include <iostream>
#include   <fstream>
#include  <cstdlib>
#include  <cstring>
#include  <cassert>
#include   <cstdio>
#include   <vector>
#include   <string>
#include    <cmath>
#include    <queue>
#include    <stack>
#include      <set>
#include      <map>
using namespace std;
#define P(a,b,c) make_pair(a,make_pair(b,c))
#define rep(i,a,n) for (int i=a;i<=n;i++)
#define per(i,a,n) for (int i=n;i>=a;i--)
#define CLR(vis) memset(vis,0,sizeof(vis))
#define MST(vis,pos) memset(vis,pos,sizeof(vis))
#define pb push_back
#define mp make_pair
#define all(x) (x).begin(),(x).end()
#define fi first
#define se second
#define SZ(x) ((int)(x).size())
typedef pair<int,pair<int,int> >pii;
typedef long long ll;
typedef unsigned long long ull;
const ll mod = 1000000007;
const int INF = 0x3f3f3f3f;
ll gcd(ll a, ll b) {
	return b ? gcd(b, a%b) : a;
}
template<class T>inline void gmax(T &A, T B) {
	(A<B)&&(A=B);//if(B>A)A=B;
}
template<class T>inline void gmin(T &A, T B) {
	(A>B)&&(A=B);//if(B<A)A=B;
}
template <class T>
inline bool scan_d(T &ret) {
	char c;
	int sgn;
	if(c=getchar(),c==EOF) return 0; //EOF
	while(c!='-'&&(c<'0'||c>'9')) c=getchar();
	sgn=(c=='-')?-1:1;
	ret=(c=='-')?0:(c-'0');
	while(c=getchar(),c>='0'&&c<='9') ret=ret*10+(c-'0');
	ret*=sgn;
	return 1;
}
inline void outt(int x) {
	if(x>9) outt(x/10);
	putchar(x%10+'0');
}

#define inf 0x3f3f3f3f
const int maxn = 100010;
const int maxm = 1000100;
struct fuck {
	int v, w, ne;
}ed[maxm];
int n, m, cnt;
int head[maxn], dis[maxn], cur[maxn];
void init() {
	cnt = 0;
	memset(head, -1, sizeof(head));
}
void add(int u, int v, int w) {
	ed[cnt].v = v; ed[cnt].w = w;
	ed[cnt].ne = head[u]; head[u] = cnt++;
//	ed[cnt].v = u, ed[cnt].w = 0;
//	ed[cnt].ne = head[v]; head[v] = cnt++;
}
int bfs(int st, int en) {
	queue<int>q;
	memset(dis, 0, sizeof(dis));
	dis[st] = 1;
	q.push(st);
	while (!q.empty()) {
		int u = q.front(); q.pop();
		if (u == en)return 1;
		for (int s = head[u]; ~s; s = ed[s].ne) {
			int v = ed[s].v;
			if (dis[v] == 0 && ed[s].w > 0) {
				dis[v] = dis[u] + 1; q.push(v);
			}
		}
	}
	return dis[en] != 0;
}
int dfs(int st, int en, int flow) {
	int ret = flow, a;
	if (st == en || flow == 0)return flow;
	for (int &s = cur[st]; ~s; s = ed[s].ne) {
		int v = ed[s].v;
		if (dis[v] == dis[st] + 1 && (a = dfs(v, en, min(ret, ed[s].w)))) {
			ed[s].w -= a;
			ed[s ^ 1].w += a;
			ret -= a;
			if (!ret)break;
		}
	}
	if (ret == flow)dis[st] = 0;
	return flow - ret;
}
int dinic(int st, int en) {
	int ans = 0;
	while (bfs(st, en)) {
		for (int s = 1; s <= n; s++) 
			cur[s] = head[s];
		ans += dfs(st, en, inf);
	}
	return ans;
}
int main() {
	int T;
	scan_d(T);
	int s,t;
	while(T--) {
		init();
		scanf("%d%d", &n, &m);
		int x;
		int maxx = 0;
		int minx = INF;
		rep(i,1,n) {
			scan_d(x);
			if (x<minx) {
				minx=x;
				s=i;
			}
			if (x>maxx) {
				maxx=x;
				t=i;
			}
			scan_d(x);
		}
		int u,v,w;
		rep(i,1,m){
			scanf("%d%d%d", &u,&v,&w);
			add(u,v,w);
			add(v,u,w);
		}
		int maxflow = dinic(s,t);
		printf("%d\n", maxflow);
	}
	return 0;
}