CF 1077D - Cutting Out （二分）

http://codeforces.com/contest/1077/problem/D

一直不理解check内第二重循环的意思，突然一下想通了。。好像有点犯蠢

//D - Cutting Out CodeForces - 1077D 
#include <bits/stdc++.h>
using namespace std;

const int maxn = 2e5+10;
map<int,int> m;
vector<int> s;
vector<int> ans;
int check(int cnt)
{
    //二分遍历查找合适的取出个数 
    // cnt为取出的个数 
    ans.clear();
    for(int i = 0; i < s.size(); i++){
        int w = m[s[i]] / cnt;   // 如果一个数字可以取出多次，就取多次 
        for(int j = 1; j <= w; j++){
            ans.push_back(s[i]);
        } 
    }
    return ans.size();
}
int main()
{
    int n, k, c = -1, num;
    cin >> n >> k;
    for(int t,i = 1; i <= n; i++) {
        cin >> t;
        if(!m[t])
            s.push_back(t);
        m[t]++;
        c = max(c,m[t]);
    }
    int l = 1, r = c;
    while(l <= r) {
        int mid = (l+r)/2;
        if(check(mid) >= k) {
            l = mid+1;
            num = mid;
        } else r = mid-1;
    }
    check(num);
    for(int i = 0; i < k; i++)
        cout << ans[i] << " ";
    return 0;
}