CF1037E. Trips

题目链接

CF1037E. Trips

题解

每次删点后,对不满足要求的点拓扑

代码

#include<map>
#include<queue>
#include<vector>
#include<cstdio>
#include<algorithm>
#define rep(a,b,c) for(int a = b;a <= c;++ a)
#define gc getchar()
#define pc putchar
inline int read() {
	int x = 0,f = 1;
	char c = gc;
	while(c < '0' || c > '9') c = gc;
	while(c <= '9' && c >= '0') x = x * 10 + c - '0',c = gc;
	return x * f;
}
void print(int x) {
	if(x < 0) {
		pc('-');
		x = -x;
	}
	if(x >= 10) print(x / 10);
	pc(x % 10 + '0');
}
const int maxn = 5000007;
int n,m,k;
int d[maxn];
bool del[maxn];
using namespace std;
#define pr pair<int,int>
#define mmp make_pair
map<pr,int> mp;
struct node {
	int v,next;
} edge[maxn];
int head[maxn],num = 0;
inline void add_edge(int u,int v) {
	edge[++ num].v = v; edge[num].next = head[u];head[u] = num;
}
int ans;
int u[maxn],v[maxn];
int Ans[maxn];
queue<int>q;
void solve(int x) {
	if(d[x] >= k || del[x]) return;
	del[x] = 1;
	q.push(x);
	ans --;
	while(!q.empty()) {
		int U = q.front();
		q.pop();
		for(int i = head[U];i;i = edge[i].next) {
			int V = edge[i].v;
			if(del[V]) continue;
			if(mp.count(mmp(U,V)) == 0) d[V] --;
			if(d[V] < k) { del[V] = true;ans --; q.push(V);}
		}
	}
}
int main() {
	n = read(),m = read(); k = read();
	rep(i,1,m) {
		u[i] = read(),v[i] = read();
		add_edge(u[i],v[i]);
		add_edge(v[i],u[i]);
		d[v[i]] ++;
		d[u[i]] ++;
	}
	ans = n;
	rep(i,1,n)
		solve(i);
	mp.clear();
	for(int i = m;i >= 1;-- i) {
		Ans[i] = ans;
		if(!del[u[i]]) d[v[i]] -- ;
		if(!del[v[i]]) d[u[i]] -- ;
		mp[pr(u[i],v[i])] = 1;
		mp[pr(v[i],u[i])] = 1;
		solve(u[i]);
		solve(v[i]);
	}
	rep(i,1,m)print(Ans[i]),pc('\n');
} 
/*
500 2 3
58 102
250 411
*/