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
*/