203 - 线段树的修改

2017.9.8

总感觉自己的方法太暴力。

/**
 * 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 root: The root of segment tree.
     * @param index: index.
     * @param value: value
     * @return: 
     */
    	public void modify(SegmentTreeNode root, int index, int value) {
        // write your code here
		if(root == null){
			return;
		}
		if(index < root.start || index > root.end){
			return;
		}
		if(root.start == root.end && root.end == index){
			root.max = value;
		}
		else{
			modify(root.left, index, value);
			modify(root.right, index, value);
			root.max = Math.max(root.left.max, root.right.max);
		}
		
    }
}