(Easy Edition)

https://codeforces.com/contest/1163/problem/B1

(Hard Edition)

https://codeforces.com/contest/1163/problem/B2

题解：

C++版本一

/*
*@Author:   STZG
*@Language: C++
*/
#include <bits/stdc++.h>
#include<iostream>
#include<algorithm>
#include<cstdlib>
#include<cstring>
#include<cstdio>
#include<string>
#include<vector>
#include<bitset>
#include<queue>
#include<deque>
#include<stack>
#include<cmath>
#include<list>
#include<map>
#include<set>
//#define DEBUG
#define RI register int
#define endl "\n"
using namespace std;
typedef long long ll;
//typedef __int128 lll;
const int N=100000+10;
const int M=100000+10;
const int MOD=1e9+7;
const double PI = acos(-1.0);
const double EXP = 1E-8;
const int INF = 0x3f3f3f3f;
int t,n,m,k,p,l,r,u,v;
int ans,cnt,flag,temp,sum;
int a[N];
int b[N];
int c[N];
char str;
struct node{};
int main()
{
#ifdef DEBUG
	freopen("input.in", "r", stdin);
	//freopen("output.out", "w", stdout);
#endif
    //ios::sync_with_stdio(false);
    //cin.tie(0);
    //cout.tie(0);
    //scanf("%d",&t);
    while(~scanf("%d",&n)){
        ans=1;
        sum=0;
        for(int i=1;i<=n;i++){
            scanf("%d",&a[i]);
            if(b[a[i]]==0)sum++;
            c[b[a[i]]]--;
            b[a[i]]++;
            c[b[a[i]]]++;
            if(sum==1){
                ans=i;
                continue;
            }
            if(c[1]==1){
                if(i==1||sum==1){
                    continue;
                }
                if(c[(i-1)/(sum-1)]==sum-1)
                    ans=i;
                continue;
            }
            if(c[1]==sum){
                ans=i;
                continue;
            }
            if(i%sum==1&&c[i/sum]==sum-1&&c[i/sum+1]==1)
                ans=i;
        }
        cout<<ans<<endl;
    }

#ifdef DEBUG
	printf("Time cost : %lf s\n",(double)clock()/CLOCKS_PER_SEC);
#endif
    //cout << "Hello world!" << endl;
    return 0;
}