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Copy pathAverageOfLevelsInBinaryTree.java
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50 lines (37 loc) · 1.51 KB
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// Given a non-empty binary tree, return the average value of
// the nodes on each level in the form of an array.
// See: https://leetcode.com/problems/average-of-levels-in-binary-tree/
package leetcode.tree;
import static leetcode.util.tree.BinTreeUtil.initTree;
import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import leetcode.util.tree.TreeNode;
public class AverageOfLevelsInBinaryTree {
public List<Double> averageOfLevels(TreeNode root) {
Map<Integer, List<Integer>> avgMap = new LinkedHashMap<>();
List<Double> result = new ArrayList<>();
dfs(root, 0, avgMap);
for (int key : avgMap.keySet()) {
Double average = (avgMap.get(key))
.stream().mapToDouble(val -> val).average().orElse(0.0);
result.add(average);
}
return result;
}
private void dfs(TreeNode root, int depth, Map<Integer, List<Integer>> avgMap) {
if (root == null) return;
if (!avgMap.containsKey(depth)) {
avgMap.put(depth, new ArrayList<>());
}
avgMap.get(depth).add(root.val);
dfs(root.left, depth + 1, avgMap);
dfs(root.right, depth + 1, avgMap);
}
public static void main(String[] args) {
AverageOfLevelsInBinaryTree sln = new AverageOfLevelsInBinaryTree();
TreeNode t1 = initTree(3, 9, 20, null, null, 15, 7);
System.out.println(sln.averageOfLevels(t1));
}
}