CF1393C Pinkie Pie Eats Patty-cakes

思路：

二分+贪心。

实现：

#include<bits/stdc++.h>
using namespace std;
const int N = 100001;
int cnt[N], a[N], n;
bool check(int x)
{
    set<pair<int, int>, greater<pair<int, int>>> st; 
    for (int i = 1; i <= n; i++) cnt[i] = 0;
    for (int i = 0; i < n; i++) cnt[a[i]]++;
    for (int i = 1; i <= n; i++)
    {
        if (cnt[i]) st.insert(make_pair(cnt[i], i));
    } 
    vector<int> v;
    for (int i = 0; i < n; i++)
    {
        if (i >= x + 1)
        {
            int j = v[i - x - 1];
            if (cnt[j] > 0) st.insert(make_pair(cnt[j], j));
        }
        if (st.empty()) return false;
        auto it = st.begin();
        v.push_back(it->second);
        assert(cnt[it->second] > 0);
        cnt[it->second]--;
        st.erase(it);
    }
    return true;
}
int main()
{
    int T; cin >> T;
    while (T--)
    {
        cin >> n;
        for (int i = 0; i < n; i++) cin >> a[i];
        int l = 0, r = n - 2, res = 0;
        while (l <= r)
        {
            int m = l + r >> 1;
            if (check(m))
            {
                res = m;
                l = m + 1;
            }
            else r = m - 1;
        }
        cout << res << endl;
    }
    return 0;
}