尋找數組中第k大的數

cpp] view plain copy

 

#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int partition(int arr[], int l, int r)
{
    int x = arr[r], i = l;
    for (int j = l; j <= r - 1; j++)
    {
        if (arr[j] <= x)
        {
            swap(arr[i], arr[j]);
            i++;
        }
    }
    swap(arr[i], arr[r]);
    return i;
}

int GetKth(int* a, int low, int high,int k)
{
    int pivot;
    if (low < high)
    {
        pivot = partition(a,low,high);
        if ((pivot-low + 1) == k)
            return a[pivot];
        else if ((pivot-low + 1) > k)
            return  GetKth(a,low,pivot-1,k);
        else
            return GetKth(a, pivot+1,high, k);
    }
}
int main()
{
    int a[]={1,4,6,7,98,23,24,56};
    int n = 8, k = 3;
    cout << GetKth(a,0,7,3);


}

原文：http://blog.csdn.net/u014682691/article/details/51029582