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The structure of Segment Tree is a binary tree which each node has two attributesstart and end denote an segment / interval.
start and end are both integers, they should be assigned in following rules:
build method.start=A.left, end=(A.left + A.right) / 2.start=(A.left + A.right) / 2 + 1, end=A.right.Implement a build method with a given array, so that we can create a corresponding segment tree with every node value represent the corresponding interval max value in the array, return the root of this segment tree.
Segment Tree (a.k.a Interval Tree) is an advanced data structure which can support queries like:
See wiki:
Segment Tree
Interval Tree
Given [3,2,1,4]. The segment tree will be:
[0, 3] (max = 4) / [0, 1] (max = 3) [2, 3] (max = 4) / \ / [0, 0](max = 3) [1, 1](max = 2)[2, 2](max = 1) [3, 3] (max = 4)
/** * Definition of SegmentTreeNode: * public class SegmentTreeNode { * public int start, end, max; * public SegmentTreeNode left, right; * public SegmentTreeNode(int start, int end, int max) { * this.start = start; * this.end = end; * this.max = max * this.left = this.right = null; * } * } */ public class Solution { /** *@param A: a list of integer *@return: The root of Segment Tree */ public SegmentTreeNode build(int[] A) { // write your code here if(A == null || A.length == 0) return null; return build(A, 0, A.length - 1); } public SegmentTreeNode build(int[] A, int start, int end){ if(start == end){ return new SegmentTreeNode(start, end, A[start]); } int mid = start + (end - start) / 2; SegmentTreeNode left = build(A, start, mid); SegmentTreeNode right = build(A, mid + 1, end); SegmentTreeNode root = new SegmentTreeNode(start, end, Math.max(left.max, right.max)); root.left = left; root.right = right; return root; } }
lintcode-medium-Segment Tree Build II
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原文地址：http://www.cnblogs.com/goblinengineer/p/5356093.html
