Given a binary tree, you need to compute the length of the diameter of the tree. The diameter of a binary tree is the length of the longest path between any two nodes in a tree. This path may or may not pass through the root.
Example:
1
/ \
2 3
/ \
4 5
Return 3, which is the length of the path [4,2,1,3] or [5,2,1,3].
Note:
The length of path between two nodes is represented by the number of edges between them.
解釋下題目:
找到一棵樹里的最長路徑,該路徑可能不經過根節點
1. 遞歸
實際耗時:0ms
int globalMax = 0;
public int diameterOfBinaryTree(TreeNode root) {
helper(root);
return globalMax;
}
private int helper(TreeNode root) {
if (root == null) {
return 0;
} else {
int left = helper(root.left);
int right = helper(root.right);
globalMax = Math.max(globalMax, left + right);
return Math.max(left, right) + 1;
}
}
??思路其實跟尋找最深子樹是一樣的,只不過多了一個全局變量用來記錄一下最長的距離而已。