叶子节点的个数

size_t _GetLeefNode(Node *pRoot)
{
    if (pRoot == NULL)
        return 0;
    if (NULL == pRoot->pLeft&&NULL == pRoot->pRight)
        return 1;
    return _GetLeefNode(pRoot->pLeft) + _GetLeefNode(pRoot->pRight);
}

第K层节点的个数

size_t _Height(Node *pRoot)
{
    if (NULL==pRoot)
        return 0;
    size_t highLeft = 1+_Height(pRoot->pLeft);
    size_t highRight = 1+_Height(pRoot->pRight);
    return highLeft > highRight ? highLeft : highRight;
}
int GetKLevelNode(int k)
{
    if (k<0 || k>_Height(_pRoot))
        return -1;
    return _GetKLevelNode(_pRoot, k);
}
int _GetKLevelNode(Node *pRoot, int k)
{
    if (nullptr == pRoot)
        return 0;
    if (k == 1 )
        return 1;
    return _GetKLevelNode(pRoot->_pLeft, k-1)+_GetKLevelNode(pRoot->_pRight, k-1);
}

一个数组中有一个数字的次数超过了数组的一半，求出这个字符。

//如：int a[]={2,3,2,2,2,2,2,5,4,1,2,3}，求出超过一半的数字是2
#include<iostream>
using namespace std;
int partion(int *arr, int left, int right)
{
    int begin = left;
    int end = right;
    int key = arr[begin];
    while (begin < end)
    {
        //注意快排从如果左边选比较值，则应从右边开始比较
        while (begin < end&&arr[begin] >= key)
            --end;
        while (begin < end&&arr[begin] <= key)
            ++begin;
        swap(arr[begin], arr[end]);
    }
    swap(arr[left], arr[begin]);
    return begin;
}
int getNum(int *arr, int len)
{
    if (nullptr == arr || len <= 0)
        return -1;
    int start = 0;
    int end = len - 1;
    int mid = start+(end-start)>>1;
    int index = partion(arr, 0, end);
    while (index != mid)
    {
        if (mid > index)
        {
            start = index +1;
            index = partion(arr, start, end);
        }
        else
        {
            end = index -1;
            index = partion(arr, start, end);
        }
    }
    return arr[index];
}
int main()
{
    int arr[] = { 2, 3, 2, 2,2, 2, 5, 4, 1, 2, 3 };
    int len = sizeof(arr) / sizeof(arr[0]);
    int res = getNum(arr, len);
    cout << res << endl;
    system("pause");
}