NC_72_Tree_Mirror NC_73_MoreThanHalfNum NC_74_GET_NUMBER_OF_K

package org.example.interview.practice;

/**
 * @author xianzhe.ma
 * @date 2021/8/15
 */

public class NC_72_Tree_Mirror {

    public TreeNode Mirror (TreeNode pRoot) {
        // write code here

        if (pRoot == null) {
            return pRoot;
        }
        TreeNode left = pRoot.left;
        TreeNode right = pRoot.right;

        pRoot.right = reserver(left);
        pRoot.left = reserver(right);

        return pRoot;
    }

    private TreeNode reserver(TreeNode node) {
        if (node == null) {
            return node;
        }

        TreeNode temp = reserver(node.left);
        node.left = reserver(node.right);
        node.right = temp;

        return node;
    }


  public class TreeNode {
    int val = 0;
    TreeNode left = null;
    TreeNode right = null;
    public TreeNode(int val) {
      this.val = val;
    }
  }
}

package org.example.interview.practice;

import java.util.Arrays;

/**
 * @author xianzhe.ma
 * @date 2021/11/6
 */

public class NC_73_MoreThanHalfNum {

    public int MoreThanHalfNum_Solution(int [] array) {
        Arrays.sort(array);
        // 返回数组中间的数字
        return array[array.length / 2];
    }
}

package org.example.interview.practice;

/**
 * @author xianzhe.ma
 * @date 2021/8/14
 */

public class NC_74_GET_NUMBER_OF_K {

    public static int GetNumberOfK(int [] array , int k) {
        int index = binarySearch(array, 0, array.length-1, k);
        if (index == -1) {
            return 0;
        }

        while (index >= 0 && array[index] == k ) {
            index --;
        }
        index ++;
        int count = 0;
        while (index < array.length && array[index] == k)  {
            count++;
            index++;
        }
        return count;
    }

    public static int binarySearch(int[] array, int left, int right, int k) {
        if (left > right) {
            return -1;
        }

        int mid = (left + right) / 2;
        int value = array[mid];

        if (value == k) {
            return mid;
        }

        if (k < value) {
            return binarySearch(array, left, mid - 1, k);
        } else {
            return binarySearch(array, mid + 1, right, k);
        }

    }

    public static void main (String[] args) {
        int[] arrays = {1,2,3,3,3,3};
        int count = GetNumberOfK(arrays, 3);
        System.out.println(count);

    }
}