Java-如何根据单个int对数组进行排序

Question

Say I have an array as such:

[9, 7, 13, 24, 2, 16, 3, 10]

And I wanted to sort the array based off of the int 9, where all values less than 9 are to its left, and all values greater are to its right, could a version of selection sort be used?

A little stumped here

Answer 1

What you want should be something like one step of quick sort.

I modify a little so that you can pass an pivot needed as a parameter :

public static void main(String[] args) {
    int[] a = new int[]{9,7,13,24,2,16,3,10};
    System.out.println(partition(a,9));//use value 9 as pivot 
    System.out.println(Arrays.toString(a));

}

private static int  partition(int[] a, int pivot){
    int pivotIndex = 0;

    for(int i=0;i<a.length;i++){//find initial pivot Index
        if(a[i]==pivot) {
            pivotIndex = i;
            break;
        }
    }


    int low = 0;
    int high = a.length-1;

    while(low<high){
        while(low<high&&a[high]>=pivot) high--;
        a[pivotIndex] = a[high];
        pivotIndex = high;

        while(low<high&&a[low]<=pivot) low++;
        a[pivotIndex] = a[low];
        pivotIndex= low;
    }

    //Actual pivotIndex finded
    a[pivotIndex] = pivot;

    return pivotIndex;
}

output:

3
[3, 7, 2, 9, 24, 16, 13, 10]