dfs

  1. /**
  2.  * Definition for a binary tree node.
  3.  * function TreeNode(val, left, right) {
  4.  *     this.val = (val===undefined ? 0 : val)
  5.  *     this.left = (left===undefined ? null : left)
  6.  *     this.right = (right===undefined ? null : right)
  7.  * }
  8.  */
  9. /**
  10.  * @param {TreeNode} root
  11.  * @return {number}
  12.  */
  13. var sumNumbers = function(root) {
  14.     if (!root) return root
  15.     let arr = []
  16.     let result = 0
  17.     let dfs = (data, presum) => {
  18.         if (data) {
  19.             presum = data.val + presum * 10
  20.             if (!data.left && !data.right)
  21.                 arr.push(presum)
  22.             else {
  23.                 dfs(data.left, presum)
  24.                 dfs(data.right, presum)
  25.             }
  26.         }
  27.     }
  28.     dfs(root, 0)
  29.     result = arr.reduce((a, b) => {return a + b})
  30.     return result
  31. };

优化一下得到：

  1. /**
  2.  * Definition for a binary tree node.
  3.  * function TreeNode(val, left, right) {
  4.  *     this.val = (val===undefined ? 0 : val)
  5.  *     this.left = (left===undefined ? null : left)
  6.  *     this.right = (right===undefined ? null : right)
  7.  * }
  8.  */
  9. /**
  10.  * @param {TreeNode} root
  11.  * @return {number}
  12.  */
  13. var sumNumbers = function(root) {
  14.     let dfs = (data, presum) => {
  15.         if (data === null) return 0
  16.         presum = data.val + presum * 10
  17.         if (!data.left && !data.right) {
  18.             return presum
  19.         }
  20.         return dfs(data.left, presum) + dfs(data.right, presum)
  21.     }
  22.     return dfs(root, 0)
  23. };

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