快速排序——Java

Posted 2020-10-06 傍晚的羔羊

快排的思想想必大家都懂，前后两个指针，向中间靠拢。我这个partition函数能保证所有相同的数都被比较一次，靠拢在一起。

代码：

 

public class Main {  
    
    public static int[] partition1(int[] arr, int begin, int end, int pivotValue) {
        int small = begin-1;
        int cur = begin;
        int big = end+1;
        
        while(cur!=big) {
            if(arr[cur] < pivotValue) {
                swap(arr, ++small, cur++);
            } else if(arr[cur] > pivotValue) {
                swap(arr, cur, --big);
            } else {
                cur++;
            }
        }
        
        int[] range = new int[2];
        range[0] = small;
        range[1] = big;
        
        return range;
    }

    
    public static void quickSort(int[] array,int low, int high) {
        if(array == null || array.length==0) {
            return;
        }
        
        if(low>=high) {
            return;
        }
        
        int[] res = partition1(array, low, high, array[low]);
        quickSort(array, low, res[0]);
        quickSort(array, res[1], high);
    }
    public static void main(String[] args) {
        int[] a = {34,2,25,1,12,34,12,56,23,15,34,12,12,54,34};
        quickSort(a, 0, a.length-1);
        for(int i=0; i<a.length; i++) {
            System.err.print(a[i]+" ");
        }
    }
    
    private static void swap(int[] array, int low, int high) {
        int temp = array[low];
        array[low] = array[high];
        array[high] = temp;
    }
    
}