摘要： 此题如果 #1 和 #4判断分支交换，大集合就会超时（因为每次对于非叶子节点都要判断是不是叶子节点）。可见，有时候if else判断语句也会对于运行时间有较大的影响。import java.util.ArrayList;class TreeNode { int val; TreeNode left; TreeNode right; TreeNode(int x) { val = x; }}public class Solution { private int currSum = 0; private ArrayList> result = new Array... 阅读全文

摘要： 很简单一道题，搞错了N次，记录一下。public class Solution { private int currSum = 0; public boolean hasPathSum(TreeNode root, int sum) { if (null == root) return false; currSum = 0; return hasPathSumCore(root, sum); } public boolean hasPathSumCore(TreeNode r... 阅读全文

摘要： class ListNode { int val; ListNode next; ListNode(int x) { val = x; next = null; }}public class Solution { private ListNode left; //java不支持c++的LinkedList &*p这种方式，所以用member variable来存放left private boolean alreadyDone = false; public void reverseLinkedList... 阅读全文