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617 Merge Two Binary Trees

/**
 *
 * Ashish Patel
 * e: ashishsushilPatel@gmail.com
 * w: https://ashish.me
 *
 */

/*
 * Given two binary trees and imagine that when you put one of them to cover the other,
 * some nodes of the two trees are overlapped while the others are not.
 *
 * You need to merge them into a new binary tree. The merge rule is that if two nodes
 * overlap, then sum node values up as the new value of the merged node. Otherwise,
 * the NOT null node will be used as the node of new tree.
 */

function TreeNode(val) {
  this.val = val
  this.left = this.right = null
}

const mergeTwoBinaryTrees = (t1, t2) => {
  if (!t1) return t2
  if (!t2) return t1
  t1.val += t2.val
  t1.left = mergeTwoBinaryTrees(t1.left, t2.left)
  t1.right = mergeTwoBinaryTrees(t1.right, t2.right)
  return t1
}

test('mergeTwoBinaryTrees', () => {
  const t1 = new TreeNode(1)
  t1.right = new TreeNode(2)
  t1.left = new TreeNode(3)
  t1.left.left = new TreeNode(5)

  const t2 = new TreeNode(2)
  t2.right = new TreeNode(3)
  t2.right.right = new TreeNode(7)
  t2.left = new TreeNode(1)
  t2.left.right = new TreeNode(4)

  const t3 = new TreeNode(3)
  t3.right = new TreeNode(5)
  t3.right.right = new TreeNode(7)
  t3.left = new TreeNode(4)
  t3.left.left = new TreeNode(5)
  t3.left.right = new TreeNode(4)
  expect(mergeTwoBinaryTrees(t1, t2)).toEqual(t3)
})

Created 2020-12-05T20:22:20+05:18, updated 2020-12-05T20:23:54+05:18 · History · Edit