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
*/