Submission #9096498

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Source Code Expand

#include <bits/stdc++.h>
#define meow(args...) fprintf(stderr, args)
template<class T1, class T2> inline bool cmin(T1 &a, const T2 &b) {return b<a?(a=b, true):false;}
template<class T1, class T2> inline bool cmax(T1 &a, const T2 &b) {return a<b?(a=b, true):false;}
template<class Type> Type read() {
	Type a;
	bool b;
	unsigned char c;
	while(c=getchar()-48, (c>9)&(c!=253));
	for(a=(b=c==253)?0:c; (c=getchar()-48)<=9; a=a*10+c);
	return b?-a:a;
}
auto rd=read<int>;

const int N=2000;
int n, m, src, arg, par[N][N], mark[N][N], ans;
std::vector<int> tr[N];
std::vector<std::pair<int, int>> list;
void predfs(int u) {
	for(int v: tr[u])
		if(v!=par[src][u]) {
			par[src][v]=u;
			predfs(v);
		}
}
void dfs(int u) {
	mark[src][u]=arg;
	for(int v: tr[u])
		if(v!=par[src][u])
			if(~mark[src][v]) list.emplace_back(arg, v); else dfs(v);
}
void sol(int u, int p, int b) {
	if(mark[b][u]==u) ++ans, b=u;
	for(int v: tr[u]) if(v!=p) sol(v, u, b);
}
int main() {
	n=rd(), m=rd();
	for(int i=1; i<n; ++i) {
		int u=rd()-1, v=rd()-1;
		tr[u].push_back(v);
		tr[v].push_back(u);
	}
	for(src=0; src<n; ++src) par[src][src]=-1, predfs(src);
	for(int i=0; i<n; ++i) memset(mark[i], -1, n*sizeof(int));
	while(m--) {
		int u=rd()-1, v=rd()-1;
		list.emplace_back(u, v);
		while(!list.empty()) {
			u=list.back().first, v=list.back().second;
			list.pop_back();
			while(u!=v&&~mark[u][v]) u=mark[u][v];
			while(u!=v&&~mark[v][u]) v=mark[v][u];
			if(u==v) continue;
			src=u, dfs(arg=v);
			src=v, dfs(arg=u);
		}
	}
	for(int i=0; i<n; ++i) for(int j: tr[i]) sol(j, i, i);
	printf("%d\n", ans/2);
	return 0;
}

Submission Info

Judge Result