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月光杯:
问题解决了吗?
Exceptions in HDFS -
iostreamin:
神,好厉害,这是我找到的唯一可以ac的Java代码,厉害。
[leetcode] word ladder II -
standalone:
One answer I agree with:引用Whene ...
How many string objects are created? -
DiaoCow:
不错!,一开始对这些确实容易犯迷糊
erlang中的冒号 分号 和 句号 -
standalone:
Exception in thread "main& ...
one java interview question
Problem:
Given a binary tree, each node has an integer value attached (can be negative), write code to find the subtree with the max sum.
My solution:
Basically this is a recursive problem, for each subtree result, you should remember its maxSum and corresponding root node. So I use a struct SubTreeResult to remember all such info.
Note: The code I pasted here is not tested sufficiently, so don't take it as correct solution unless you verify it yourself.
Given a binary tree, each node has an integer value attached (can be negative), write code to find the subtree with the max sum.
My solution:
Basically this is a recursive problem, for each subtree result, you should remember its maxSum and corresponding root node. So I use a struct SubTreeResult to remember all such info.
Note: The code I pasted here is not tested sufficiently, so don't take it as correct solution unless you verify it yourself.
package alg; import java.util.ArrayList; public class MaxSumTree { class Node { int value; Node left, right; Node(int v, Node l, Node r){ value = v; left = l; right = r; } } class SubTreeResult { Node subTreeRoot, maxSumNode; int sum, maxSum; SubTreeResult(Node r, Node maxNode, int maxSum, int sum){ this.subTreeRoot = r; this.maxSumNode = maxNode; this.sum = sum; this.maxSum = maxSum; } } public SubTreeResult findMaxSubTree(Node r){ SubTreeResult leftResult = null, rightResult = null, result = null; if(r.left != null){ leftResult = findMaxSubTree(r.left); } if(r.right != null){ rightResult = findMaxSubTree(r.right); } if(leftResult != null && rightResult != null){ int sum = r.value + leftResult.sum + rightResult.sum; if(leftResult.maxSum >= rightResult.maxSum){ if(sum >= leftResult.maxSum){ result = new SubTreeResult(r, r, sum, sum); }else { result = new SubTreeResult(r, leftResult.maxSumNode, leftResult.maxSum, sum); } }else { if(sum >= rightResult.maxSum){ result = new SubTreeResult(r, r, sum, sum); }else { result = new SubTreeResult(r, rightResult.maxSumNode, rightResult.maxSum, sum); } } }else if(leftResult != null){ int sum = r.value + leftResult.sum; if(sum >= leftResult.maxSum){ result = new SubTreeResult(r, r, sum, sum); }else { result = new SubTreeResult(r, leftResult.maxSumNode, leftResult.maxSum, sum); } }else if(rightResult != null){ int sum = r.value + rightResult.sum; if(sum >= rightResult.maxSum){ result = new SubTreeResult(r, r, sum, sum); }else { result = new SubTreeResult(r, rightResult.maxSumNode, rightResult.maxSum, sum); } }else { result = new SubTreeResult(r, r, r.value, r.value); } return result; } public Node buildBinaryTree(ArrayList<Integer> list){ int size = list.size(); if(size == 0) return null; Node [] nodes = new Node[size]; for(int i = 0; i< size; i++){ int number = list.get(i); nodes[i] = new Node(number, null, null); int idx = i; if(i%2 == 0){ idx = i - 1; } if(idx > 0){ idx /= 2; if(i%2 == 0){ nodes[idx].right = nodes[i]; }else { nodes[idx].left = nodes[i]; } } } return nodes[0]; } public void printTree(Node root){ if(root != null){ System.out.println(root.value); if(root.left != null) printTree(root.left); if(root.right != null) printTree(root.right); } } /** * @param args */ public static void main(String[] args) { // TODO Auto-generated method stub MaxSumTree mst = new MaxSumTree(); ArrayList<Integer> list = new ArrayList<Integer>(); list.add(3); list.add(-4); list.add(2); list.add(7); list.add(-5); list.add(9); list.add(-8); list.add(-2); list.add(5); list.add(20); list.add(100); list.add(-30); list.add(-150); Node root = mst.buildBinaryTree(list); mst.printTree(root); SubTreeResult str = mst.findMaxSubTree(root); System.out.println("max sum subtree root:" + str.maxSumNode.value + ", max sub:" + str.maxSum); } }
发表评论
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ssl 与 java 实例
2014-01-27 10:10 830http://www.iteye.com/topic/1125 ... -
Java NIO
2014-01-10 21:28 743看了这个java nio的教程,明白了什么是Selector. ... -
再谈Java的wait(), sleep(), notify()和notifyAll()
2013-07-25 10:59 1938一段时间不用java,这些概念就全混淆了,有必要彻底澄清一下, ... -
Why singleton is anti-pattern?
2013-07-03 10:12 909OO Test Other reasons? -
How to generate the serialVersionUID when you implement Serializable interface,j
2013-07-01 10:52 985http://docs.oracle.com/javase/6 ... -
Java Override的两个问题
2013-06-01 11:40 9771: 如果子类中的方法的参数是父类的方法的子类型,那么算不算o ... -
Java常用类API统计
2013-06-01 11:35 0String charAt(int) compareTo( ... -
How many string objects are created?
2013-06-01 10:18 1354This is a very common java inte ... -
使用Java的DelayQueue容易碰到的一个坑
2013-05-27 17:32 6779今天不忙,学习一下java.util.concurrent.D ... -
[leetcode] Balanced Binary Tree
2013-04-28 14:08 1614Check if a binary tree is balan ... -
[leetcode] find median of two sorted arrays
2013-04-26 10:55 1496http://leetcode.com/onlinejudge ... -
[leetcode] word ladder
2013-04-25 15:05 2305Q: Given two words (start and ... -
[leetcode] word ladder II
2013-04-15 07:35 12085http://leetcode.com/onlinejudge ... -
[leetcode] Count and Say
2013-04-12 14:05 2276http://leetcode.com/onlinejudge ... -
Date/Time处理函数总结 [To Do]
2013-04-12 10:46 694几种我所用到的用来处理日期,时间的函数总结。 Perl 1 ... -
[leetcode] Palindrome Partition
2013-04-12 10:25 1341http://leetcode.com/onlinejudge ... -
[leetcode] Palindrome Partitioning II
2013-04-11 16:45 1545http://leetcode.com/onlinejudge ... -
Profiling your Java code using Spring
2013-03-05 15:02 728Quite good article!!! http://w ... -
Java的Generics的几点限制
2012-12-28 15:00 4791参见 http://docs.oracle.com/ ... -
Overriding Method Using Parameter That is a Subclass?
2012-12-27 22:14 928参见 http://www.coderanch.com/t/3 ...
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