You don't need to read input or print anything. Your task is to complete the function leftLeavesSum() which takes the root node of the tree as input and returns the sum of all the left leaf nodes present in the given binary tree.
Expected Time Complexity: O(N). Expected Auxiliary Space: O(Height of the Tree).
1<=Number of nodes<=105
Note:The Input/Ouput format and Example given are used for system's internal purpose, and should be used by a user for Expected Output only. As it is function problem, hence a user should not read any input from stdin/console. The task is to complete the function specified, and not to write the full code.