[LintCode] Segment Tree Build 建立线段树
2016-07-11 10:00
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The structure of Segment Tree is a binary tree which each node has two attributes
start and end are both integers, they should be assigned in following rules:
The root's start and end is given by
The left child of node A has
The right child of node A has
if start equals to end, there will be no children for this node.
Implement a
Have you met this question in a real interview?
Yes
Clarification
Segment Tree (a.k.a Interval Tree) is an advanced data structure which can support queries like:
which of these intervals contain a given point
which of these points are in a given interval
See wiki:
Segment Tree
Interval Tree
Example
Given
Given
这道题让我们建立线段树,也叫区间树,是一种高级树结构,但是题目中讲的很清楚,所以这道题实现起来并不难,我们可以用递归来建立,写法很简单,参见代码如下:
startand
enddenote 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 has
start=A.left, end=(A.left + A.right) / 2.
The right child of node A has
start=(A.left + A.right) / 2 + 1, end=A.right.
if start equals to end, there will be no children for this node.
Implement a
buildmethod with two parameters startand 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.
Have you met this question in a real interview?
Yes
Clarification
Segment Tree (a.k.a Interval Tree) is an advanced data structure which can support queries like:
which of these intervals contain a given point
which of these points are in a given interval
See wiki:
Segment Tree
Interval Tree
Example
Given
start=0, end=3. The segment tree will be:
[0, 3] / \ [0, 1] [2, 3] / \ / \ [0, 0] [1, 1] [2, 2] [3, 3]
Given
start=1, end=6. The segment tree will be:
[1, 6] / \ [1, 3] [4, 6] / \ / \ [1, 2] [3,3] [4, 5] [6,6] / \ / \ [1,1] [2,2] [4,4] [5,5]
这道题让我们建立线段树,也叫区间树,是一种高级树结构,但是题目中讲的很清楚,所以这道题实现起来并不难,我们可以用递归来建立,写法很简单,参见代码如下:
class Solution { public: /** *@param start, end: Denote an segment / interval *@return: The root of Segment Tree */ SegmentTreeNode * build(int start, int end) { if (start > end) return NULL; SegmentTreeNode *node = new SegmentTreeNode(start, end); if (start < end) { node->left = build(start, (start + end) / 2); node->right = build((start + end) / 2 + 1, end); } return node; } };
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