数据结构-数组中出现次数超过一半的数字

#include <iostream>

using namespace std;

void QickSort(int *a,int n,int low,int high){
    int i=low;
    int j=high;
    int tmp = a[i];

    if(j <= i){
        return;
    }

    while(j !=  i){
        while(a[j] >= tmp && j > i){
            j--;
        }
        a[i] = a[j];
        while(a[i] <= tmp && j > i){
            i++;
        }
        a[j] = a[i];
    }
    a[i] = tmp;

    QickSort(a,n,low,i-1);
    QickSort(a,n,i+1,high);
}

int CountThanHalf(int* a,int n){
    if(a == NULL || n <= 0){
        return 0;
    }

    int low = 0;
    int high = n-1;

    QickSort(a,n,low,high);

    int count = 0;
    int tmp = a[n/2];
    for(int i=0;i<n;i++){
        if(a[i] == tmp){
            count++;
        }
    }

    if(count >= n/2){
        return tmp;
    }
    else{
        return 0;
    }
}

int main()
{
    int a[] = {1,2,3,2,2,2,5,4,2};
    int n = sizeof(a)/sizeof(*a);

    int result = CountThanHalf(a,n);

    cout << result << endl;

    return 0;
}