Day-24-Sum of Left Leaves.cpp

Find the sum of all left leaves in a given binary tree.

Example:

    3
   / \
  9  20
    /  \
   15   7

There are two left leaves in the binary tree, with values 9 and 15 respectively. Return 24.









/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    int sum=0;
    void inorder(TreeNode *root){
        if(!root) return;
        if(root->left){
            if(root->left->left==NULL && root->left->right==NULL){
                sum+=root->left->val;
            }
        }
        inorder(root->left);
        inorder(root->right);
    }

    int sumOfLeftLeaves(TreeNode* root) {
        inorder(root);
        return sum;
    }
};