# Segment Tree Modify

Source: Internet
Author: User

For a `Maximum Segment Tree` , which each node have an extra value to `max` store the maximum value in this node ' s interval.

Implement a `modify` function with three parameter `root` , and to change the `index` `value` node's value with[start, end] = [I Ndex, index] to the new given value. Make sure the Every node in segment tree still have the Max attribute with the correct value.

Example

For segment tree:

``                      [1, 4, max=3]                    /                        [1, 2, max=2]                [3, 4, max=3]       /              \             /             [1, 1, max=2], [2, 2, max=1], [3, 3, max=0], [4, 4, max=3]``

If call `modify(root, 2, 4)` , we can get:

``                      [1, 4, max=4]                    /                        [1, 2, max=4]                [3, 4, max=3]       /              \             /             [1, 1, max=2], [2, 2, max=4], [3, 3, max=0], [4, 4, max=3]``

or call `modify(root, 4, 0)` , we can get:

``                      [1, 4, max=2]                    /                        [1, 2, max=2]                [3, 4, max=0]       /              \             /             [1, 1, max=2], [2, 2, max=1], [3, 3, max=0], [4, 4, max=0]``
`1 /**2 * Definition of Segmenttreenode:3 * public class Segmenttreenode {4 * public int start, end, Max;5 * Public Segmenttreenode left and right;6 * Public Segmenttreenode (int start, int end, int max) {7 * This.start = start;8 * this.end = end;9 * This.max = MaxTen * This.left = This.right = null; One  *     } A  * } -  */ -  Public classSolution { the     /** - * @param root, index, value:the root of segment tree and - *@ Change the node's value with [Index, index] to the new given value - * @return: void +      */ -      Public voidModify (Segmenttreenode root,intIndexintvalue) { + changeandupdate (root, index, value); A     } at      -     Private voidChangeandupdate (Segmenttreenode root,intIndexintvalue) { -         if(Root.start = = Index && Root.end = =index) { -Root.max =value; -             return; -         } in          -         intMid = (Root.start + root.end)/2;  to         if(Mid >=index) { + Change (root.left, index, value); -}Else { the Change (root.right, index, value); *         } \$Root.max =Math.max (Root.left.max, Root.right.max);Panax Notoginseng     } -}`

Segment Tree Modify

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