Mock Test: Microsoft #6

Trim a Binary Search Tree

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    public TreeNode trimBST(TreeNode root, int low, int high) {
        //end case
        if (root == null) {
            return root;
        }
        
        //val이 high보다 크면 오른쪽에 있는 것들은 다 현재 val보다도 클테니 냅다버리고 왼쪽으로 가야함
        
        if (root.val > high) {
            return trimBST(root.left, low, high);
        }
        
        //val이 low보다 작으면 왼쪽것들은 너무 작으니 냅다 오른쪽으로 감
        if (root.val < low) {
            return trimBST(root.right, low, high);
        }
        
        root.left = trimBST(root.left, low, high);
        root.right = trimBST(root.right, low, high);
        
        return root; 
        
        
    }

}

Add Two Numbers II

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        ListNode l1r = reverse(l1);
        ListNode l2r = reverse(l2);
        
        ListNode cur1 = l1r;
        ListNode cur2 = l2r;
        int carry = 0;
        ListNode result = new ListNode(-1); 
        ListNode cur = result;
        
        while (cur1 != null && cur2 != null) {
            int val = carry + cur1.val + cur2.val;
            carry = val / 10;
            val = val % 10; 
            
            cur.next = new ListNode(val);
            cur1 = cur1.next;
            cur2 = cur2.next;
            cur = cur.next;
        }
        
        while (cur1 != null) {
            int val1 = carry + cur1.val;
            carry = val1 / 10;
            val1 = val1 % 10;
            cur.next = new ListNode(val1);
            cur = cur.next;
            cur1 = cur1.next;
        } 
        
        while (cur2 != null) {
            int val2 = carry + cur2.val;
            carry = val2 / 10;
            val2 = val2 % 10;
            cur.next = new ListNode(val2);
            cur = cur.next;
            cur2 = cur2.next; 
        }
        
        if (carry != 0) {
            cur.next = new ListNode(1);
        }
        
        return reverse(result.next);
    }
    
    private ListNode reverse(ListNode n) {
        ListNode prev = null;
        ListNode cur = n;
        ListNode next = null;
        
        while (cur != null) {
            next = cur.next;
            cur.next = prev;
            prev = cur;
            cur = next; 
        }
        n = prev;
        return n; 
    }
}