Luogu 3376（最大流）（Dinic+当前弧优化）

传送门

Dinic+当前弧优化，复杂度上界为O(V^2*E)，NOIP应该还不至于卡这个而支持ISAP吧。

#include
#include
#include
#include
#include
using namespace std;
const int N=1e4+4,M=1e5+4,INF=0x3f3f3f3f;
int n,m,source,sink;
int head[N],etot=0;
struct EDGE {
	int v,nxt,w,r;
}e[M<<1];
int dis[N],cur[N];
inline int read() {
	int x=0;char c=getchar();
	while (c<'0'||c>'9') c=getchar();
	while (c>='0'&&c<='9') x=(x<<3)+(x<<1)+c-'0',c=getchar();
	return x;
}
inline void adde(int u,int v,int r) {
	e[etot].nxt=head[u],e[etot].v=v,e[etot].r=r,head[u]=etot++;
	e[etot].nxt=head[v],e[etot].v=u,e[etot].r=0,head[v]=etot++;
}
inline bool bfs() {
	queue q;
	memset(dis,-1,sizeof(dis));
	q.push(source),dis[source]=0;
	while (!q.empty()) {
		int p=q.front();
		q.pop();
		for (int i=head[p];~i;i=e[i].nxt) {
			int v=e[i].v;
			if (e[i].r>0&&dis[v]==-1)
				q.push(v),dis[v]=dis[p]+1;
		}
	}
	return ~dis[sink];
}
int dfs(int p,int low) {
	if (p==sink||low==0) return low;
	int cost=0,flow;
	for (int &i=cur[p];~i;i=e[i].nxt) {
		int v=e[i].v;
		if (e[i].r>0&&dis[v]==dis[p]+1&&(flow=dfs(v,min(low,e[i].r)))) {
			e[i].r-=flow;
			e[i^1].r-=flow;
			cost+=flow;
			low-=flow;
			if (low==0) return cost;
		}
	}
	if (low>0) dis[p]=-1;
	return cost;
}
int main() {
//	freopen("P3376.in","r",stdin);
	memset(head,-1,sizeof(head));
	n=read(),m=read(),source=read(),sink=read();
	for (register int i=0;i