BJFUOJ-302

数组的主元素查询

#include <iostream>
#include <vector>
#include <unordered_map>
using namespace std;

int find_main(vector<int>v){
    unordered_map<int,int>HashMap;
    for(vector<int>::iterator it = v.begin();it!=v.end();it++){
        if(HashMap.find(*it) != HashMap.end()){
            HashMap[*it]++;
        }else{
            HashMap[*it] = 1;
        }
    }
    int res = -1;
    int resNum = 0;
    for(auto it:HashMap){
        if(it.second > res){
            res = it.second;
            resNum = it.first;
        }
    }

    if(res > v.size()/2){
        return resNum;
    }else return -1;
}

int main(){

    int n;
    while(cin >> n && n!=0){
        vector<int>v;
        for(int i = 0;i<n;i++){
            int x;
            cin>>x;
            v.push_back(x);
        }
        cout<<find_main(v)<<endl;
    }

    return 0;
}