Lintcode - Segment Tree Build - 雯雯熊孩子 - 博客频道 - CSDN.NET

Lintcode - Segment Tree Build - 雯雯熊孩子 - 博客频道 - CSDN.NET

The structure of Segment Tree is a binary tree which each node has two attributes start andend denote an segment / interval.

start and end are both integers, they should be assigned in following rules:

• The root's start and end is given by buildmethod.
• The left child of node A hasstart=A.left, end=(A.left + A.right) / 2.
• The right child of node A hasstart=(A.left + A.right) / 2, end=A.right.
• if start equals to end, there will be no children for this node.

Implement a build method with two parameters start and end, so that we can create a corresponding segment tree with every node has the correct start and end value, return the root of this segment tree.

 * public class SegmentTreeNode {
 *     public int start, end;
 *     public SegmentTreeNode left, right;
 *     public SegmentTreeNode(int start, int end) {
 *         this.start = start, this.end = end;
 *         this.left = this.right = null;
 *     }
 * }
    public SegmentTreeNode build(int start, int end) {
        // write your code here
        if (start > end) {
            return null;
        }
        SegmentTreeNode node = new SegmentTreeNode(start, end);
        if (start == end) {
            return node;
        }
        int m = start + (end-start)/2;
        node.left = build(start, m);
        node.right = build(m+1, end);
        return node;
    }

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