5. Kth Largest Element

最新推荐文章于 2022-05-08 00:37:03 发布

foradawn

最新推荐文章于 2022-05-08 00:37:03 发布

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分类专栏： LintCode 文章标签： Quick Sort

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本文介绍了一种使用快速排序算法来查找数组中第K大的元素的方法。通过具体示例展示了如何实现这一算法，并提供了完整的代码实现。

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5. Kth Largest Element

Description

Find K-th largest element in an array.

Example

In array [9,3,2,4,8], the 3rd largest element is 4.
In array [1,2,3,4,5], the 1st largest element is 5, 2nd 
largest element is 4, 3rd largest element is 3 and etc.

Solution

//emmm，暂时就采用快排吧，以后有机会再补充
class Solution {
    /*
     * @param k : description of k
     * @param nums : array of nums
     * @return: description of return
     */
    public int kthLargestElement(int k, int[] nums) {
        // write your code here
        if(nums.length == 0 || k>nums.length) return 0;
        quick_sort(nums,0,nums.length-1);
        return nums[k-1];
    }

    private void quick_sort(int[] nums,int q,int r){
        if(nums.length == 0) return;
        if(q<r){
            int p = partition(nums,q,r);
            quick_sort(nums,q,p-1);
            quick_sort(nums,p+1,r);
        }
    }

    private int partition(int[] nums,int q,int r){
        int i = q,j = r;
        int x = nums[q];
        while(i<j){
            while(nums[j]<=x&&i<j) j--;
            nums[i] = nums[j];
            while(nums[i]>=x&&i<j) i++;
            nums[j] = nums[i];
        }
        nums[i] = x;
        return i;
    }

};