zoukankan      html  css  js  c++  java
  • Lintcode: Segment Tree Query

    For an integer array (index from 0 to n-1, where n is the size of this array), in the corresponding SegmentTree, each node stores an extra attribute max to denote the maximum number in the interval of the array (index from start to end).
    
    Design a query method with three parameters root, start and end, find the maximum number in the interval [start, end] by the given root of segment tree.
    
    Have you met this question in a real interview? Yes
    Example
    For array [1, 4, 2, 3], the corresponding Segment Tree is:
    
                      [0, 3, max=4]
                     /             
              [0,1,max=4]        [2,3,max=3]
              /                 /         
       [0,0,max=1] [1,1,max=4] [2,2,max=2], [3,3,max=3]
    query(root, 1, 1), return 4
    
    query(root, 1, 2), return 4
    
    query(root, 2, 3), return 3
    
    query(root, 0, 2), return 4

    这道题的启示是:Segment Tree 不光是可以找线段和,还可以找线段max, min等各种各样的指标

     1 /**
     2  * Definition of SegmentTreeNode:
     3  * public class SegmentTreeNode {
     4  *     public int start, end, max;
     5  *     public SegmentTreeNode left, right;
     6  *     public SegmentTreeNode(int start, int end, int max) {
     7  *         this.start = start;
     8  *         this.end = end;
     9  *         this.max = max
    10  *         this.left = this.right = null;
    11  *     }
    12  * }
    13  */
    14 public class Solution {
    15     /**
    16      *@param root, start, end: The root of segment tree and 
    17      *                         an segment / interval
    18      *@return: The maximum number in the interval [start, end]
    19      */
    20     public int query(SegmentTreeNode root, int start, int end) {
    21         // write your code here
    22         if (root.start==start && root.end==end) return root.max;
    23         int mid = (root.start+root.end)/2;
    24         if (end <= mid) return query(root.left, start, end);
    25         else if (start > mid) return query(root.right, start, end);
    26         else return Math.max(query(root.left, start, mid), query(root.right, mid+1, end));
    27     }
    28 }
  • 相关阅读:
    一目了然卷积神经网络
    浅析 MVC Pattern
    程序员读书清单
    “数据中台”的再思考
    火锅、报表与数据库的故事
    从NoSQL到NewSQL,谈交易型分布式数据库建设要点
    从架构特点到功能缺陷,重新认识分析型分布式数据库
    YCSB测试HBase远程完全分布式集群
    NoSQL性能测试工具YCSB-Running a Workload
    再谈数据库事务隔离性
  • 原文地址:https://www.cnblogs.com/EdwardLiu/p/5174352.html
Copyright © 2011-2022 走看看