CF140C New Year Snowmen

Posted 2020-11-29 cjoiershiina-mashiro

题目
还是贪心。
每次选择出现次数最多的三个直径。
正确性感觉比较显然。

#include<bits/stdc++.h>
using namespace std;
int read(){int x=0,c=getchar();while(!isdigit(c))c=getchar();while(isdigit(c))x=x*10+c-48,c=getchar();return x;}
const int N=100007;
struct node{int num,x;}a,b,c;
int operator<(node a,node b){return a.num<b.num;}
int t[N],cnt[N],r[N],num[3];priority_queue<node>q;vector<tuple<int,int,int>>ans;
int main()
{
    int n=read(),i,m=n;
    for(i=1;i<=n;++i) t[i]=r[i]=read();
    sort(t+1,t+m+1),m=unique(t+1,t+m+1)-t-1;
    for(i=1;i<=n;++i) ++cnt[lower_bound(t+1,t+m+1,r[i])-t];
    for(i=1;i<=m;++i) if(cnt[i]) q.push((node){cnt[i],t[i]});
    while(q.size()>=3)
    {
    a=q.top(),q.pop(),b=q.top(),q.pop(),c=q.top(),q.pop();
    num[0]=a.x,num[1]=b.x,num[2]=c.x,sort(num,num+3,greater<int>());
    ans.push_back(make_tuple(num[0],num[1],num[2]));
    --a.num,--b.num,--c.num;
    if(a.num) q.push(a);
    if(b.num) q.push(b);
    if(c.num) q.push(c);
    }
    printf("%d
",ans.size());
    for(auto x:ans) printf("%d %d %d
",get<0>(x),get<1>(x),get<2>(x));
}