找到第k小的数（快速排序思想实现）

开始

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public class FindKth {
    public int findKth(int[] arr, int left, int right, int k) {
        int i;
        if (left > right) {
            return -1;
        } else {
            i=partion(arr, left, right);
            if (i-left+1 == k) {
                return arr[i];
            } else if (i-left+1 > k) {
                return findKth(arr, left, i - 1, k);
            } else {
                return findKth(arr, i + 1, right, k-i-1);
            }
        }
    }
    public int partion(int[] arr, int left, int right) {
        int t;
        int i = left, j = right;
        int tmp = arr[left];
        while (i != j) {
            while (arr[j] >= tmp && i < j) {
                j--;
            }
            while (arr[i] <= tmp && i < j) {
                i++;
            }
            if (i < j) {
                t = arr[i];
                arr[i] = arr[j];
                arr[j] = t;
            }
        }
        arr[left]=arr[i];
        arr[i]=tmp;
        return i;
    }
    public static void main(String[] args) {
        int[] arr = { 2, 1, 55, 62, 13, 41, 22, 8, 77, 82, 16, 33 };
        System.out.println(new FindKth().findKth(arr, 0, arr.length - 1, 3));
    }
}

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结束