BZOJ 3498: PA2009 Cakes 一类经典的三元环计数问题

首先引入一个最常见的经典三元环问题。

#include 
using namespace std;
const int maxn = 100005;
vector  g[maxn], low, high;
map  mp[maxn];
int n, m, in[maxn], vis[maxn];

int main()
{
    scanf("%d %d", &n,&m);
    for(int i=1; i<=m; i++){
        int x,y;
        scanf("%d %d", &x,&y);
        g[x].push_back(y);
        g[y].push_back(x);
        mp[x][y] = 1;
        mp[y][x] = 1;
        in[x]++;
        in[y]++;
    }
    for(int i=1; i<=n; i++){
        if(in[i]<=sqrt(m)) low.push_back(i);
        else high.push_back(i);
    }
    int ans = 0;
    memset(vis, false, sizeof(vis));
    for(int i=0; i

 BZOJ 3948

//BZOJ 3498
#include 
using namespace std;
const int maxn = 100005;
typedef long long LL;
struct node{
    int val,id;
    node(){}
    node(int val,int id):val(val),id(id){}
    bool operator<(const node &rhs)const{
        return val>rhs.val;
    }
}a[maxn];
vector  G[maxn];
map  mp[maxn];
int Rank[maxn], out[maxn], linker[maxn];
int n, m;

int main()
{
    scanf("%d %d", &n,&m);
    for(int i=1; i<=n; i++){
        scanf("%d", &a[i].val);
        a[i].id = i;
    }
    sort(a+1, a+n+1);
    for(int i=1; i<=n; i++) Rank[a[i].id] = i;
    for(int i=1; i<=m; i++){
        int x, y;
        scanf("%d %d", &x,&y);
        if(Rank[x]sqrt(m)+1){
                for(int k=0; k

 

转载于:https://www.cnblogs.com/spfa/p/7495438.html