算法导论算法，来实现查找第 i 小的数，不能正常工作
#include<stdio.h>
#include<stdlib.h>
#include<time.h>
int randomized_select(int *arr, int start, int end, const int i);
//int pivot;
int main()
{
int a[10] = {1, 9, 4, 3, 8, 2, 5, 6, 10, 7};
//printf("%d", randomized_select(a, 0, 9, 2) );
int num = randomized_select(a, 0, 9, 2);
return 0;
}
/*
* 返回数组 arr 下标 start 至 end 中第 i小的元素
*/
int randomized_select(int *arr, int start, int end, int i)
{
if(start == end)
{
return arr[start];
}
srand( ( unsigned )time(NULL) );
int pivot = start + rand() % (end - start);
//int pivot = rand() % (end - start + 1 ) + start; // 主元
int k = pivot - start + 1;
if(i == k) // the pivot value is the answer.
{
return arr[pivot];
}
else if(i < k)
{
return randomized_select(arr, start, pivot - 1, i);
}
else//(i >= k)
{
return randomized_select(arr, pivot + 1 , end, i - k);
}
}
