Grokking Tree Coding Patterns for Interviews
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Sum of Root To Leaf Binary Numbers (easy)
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Problem Statement

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Problem Statement

You are given the root of a binary tree, where each node holds either a 0 or 1. Each path from the root to a leaf forms a binary number.

For example, if the path is 1 -> 0 -> 1, then this could represent 101 in binary, which is 5 in decimal representation. You need to consider all these root-to-leaf paths, convert them to binary numbers and sum them.

Return the total sum of all these binary numbers.

The test cases are generated so that the answer fits in a 32-bits integer.

Examples

Example 1

  • Input: root = [1,0,1,0,1,null,1]
Image
  • Expected Output: 16
  • Explanation: The paths from the root to leaves represent binary numbers 100, 101, and 111. Their decimal equivalents are 4, 5, and 7, respectively. The sum of these numbers is 4 + 5 + 7 = 16.

Example 2

  • Input: root = [1,1,0,1,1,0,1]
Image
  • Expected Output: 23
  • Explanation: The paths represent binary numbers 111, 111, 100 and 101. Their decimal equivalents are 7, 5, 4, and 5, respectively. The sum is 7 + 7 + 4 + 5 = 23.

Example 3

  • Input: root = [1,0,1,null,null,0,1]
Image
  • Expected Output: 15
  • Explanation: The paths represent binary numbers 10, 110, and 111. Their decimal equivalents are 2, 6, and 7, respectively. The sum is 2 + 6 + 7 = 15.

Constraints:

  • The number of nodes in the tree is in the range [1, 1000].
  • Node.val is 0 or 1.

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Python3
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Problem Statement

Examples

Try it yourself