编辑代码

#include <stdio.h>  
  
void swap(int* a, int* b) {  
    int t = *a;  
    *a = *b;  
    *b = t;  
}  
  
int partition(int arr[], int low, int high) {  
    int pivot = arr[high];  
    int i = (low - 1);  
  
    for (int j = low; j <= high - 1; j++) {  
        if (arr[j] < pivot) {  
            i++;  
            swap(&arr[i], &arr[j]);  
        }  
    }  
    swap(&arr[i + 1], &arr[high]);  
    return (i + 1);  
}  
  
int quickSelect(int arr[], int low, int high, int k) {  
    if (low == high) {  
        return arr[low];  
    }  
  
    int pi = partition(arr, low, high);  
  
    if (pi == k - 1) {  
        return arr[pi];  
    } else if (pi < k - 1) {  
        return quickSelect(arr, pi + 1, high, k);  
    } else {  
        return quickSelect(arr, low, pi - 1, k);  
    }  
}  
  
int main() {  
    int arr[] = {11,8,3,9,7,1,2,5};  
    int n = sizeof(arr) / sizeof(arr[0]);  
    int k = 4; // 要查找第4大的元素  
  
    int result = quickSelect(arr, 0, n - 1, k);  
    printf("第%d大的元素是：%d\n", k, result);  
  
    return 0;  
}