[663. Equal Tree Partition] #leetcode

663_0827.java

class Solution {
    public boolean checkEqualTree(TreeNode root) {
        Map<Integer, Integer> map = new HashMap<Integer, Integer>();
        int sum = subtreeSum(root, map);
        
        if (sum == 0) return map.getOrDefault(sum, 0) > 1;
        
        return sum%2 == 0 && map.containsKey(sum/2);
    }
    
    private int subtreeSum(TreeNode node, Map<Integer, Integer> map) {
        if ( node == null ) return 0;
        int cur = node.val + subtreeSum(node.left, map) + subtreeSum(node.right, map);
        
        map.put(cur, map.getOrDefault(cur, 0) + 1);
        return cur;
    }
}