Leetcode 617. Merge Binary Trees

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Topic

Given binary trees and imagine that's when you put one of the them to cover the other, some nodes of the and trees is Overl Apped while the others is not.

You need to the merge them into a new binary tree. The merge rule is so if the nodes overlap, then sum node values up as the new value of the merged node. Otherwise, the not NULL node would be used as the node of the new tree.

Example 1:

Input:     Tree 1                     Tree 2                            1                         2                                      / \                       / \                                    3   2                     1   3                               /                           \   \                            5                             4   7                  Output: Merged tree:         3        / \       4   5      / \   \      5   4   7

Note:the merging process must start from the root nodes of both trees.

Answer:

Golang version is written by himself, the other is quoted Cain_huang, the end of the text attached link

Version Golang, test included

Mergetrees.go

 package _617_mergetreesimport ' FMT '/** * Definition for a binary tree node. * Type TreeNode struct {* Val int * Left *treenode * Right *treenode *} */type TreeNode struct {Val int left *treenode right *treenode }func Initnode (Val int, left *treenode, right *treenode) (ret *treenode) {ret = new (TreeNode) ret. val = val Ret. left = left ret. right = right return Ret}func treeprint (T1 *treenode) {if nil = = T1 {fmt. PRINTF ("null,") return} else {fmt. Printf ("%+v,", T1. Val)} treeprint (t1. left) Treeprint (t1. right)}func mergetrees (T1 *treenode, T2 *treenode) (T3 *treenode) {if nil = = T1 && Nil = = T2 {return n Il} if nil! = T1 && nil = t2{return T1}else if nil = T1 && nil! = t2 {RET Urn T2} else {t1. Val + = t2. Val t1. left = mergetrees (t1. Left, T2. left) t1. right = Mergetrees (t1. Right, T2. right)} return T1}  

Mergetrees_test.go

Package _617_mergetreesimport ("Testing" "FMT") func treeequal (T1 *treenode, T2 *treenode) bool{if T1. Val! = t2. Val {return false} if nil = = T1. Left && nil! = t2. Left {return false}else if nil! = t1. Left && nil = = t2. Left {return false} else if nil! = t1. Left && nil! = t2. Left {left: = treeequal (t1. Left, T2. left) if!left {return false}} if nil = = T1. Right && nil! = t2. Right {return false}else if nil! = t1. Right && nil = = t2. Right {return false}else if nil! = t1. Right && nil! = t2. Right {right: = treeequal (t1. Right, T2. right) if!right {return false}} return True}func test_mergetrees (t *testing. T) {t1l2: = Initnode (5, nil, nil) t1l1: = Initnode (3, T1L2, nil) T1r1: = Initnode (2, nil, nil) T1: = Initnode (1, T1L1, t1r1) T2l2r1: = Initnode (4, nil, nil) t2l2r2: = InitnodE (7, nil, nil) t2l1r1: = Initnode (1, Nil, t2l2r1) T2L1R2: = Initnode (3, nil, t2l2r2) t2: = Initnode (2, T2L1R1, T2 L1R2) T3l2r1: = Initnode (5, nil, nil) t3l2r2: = Initnode (4, nil, nil) T3l2r3: = Initnode (7, nil, nil) T3L1R1: = Initnode (4, T3L2R1, t3l2r2) T3L1R2: = Initnode (5, Nil, t3l2r3) T3: = Initnode (3, T3L1R1, T3L1R2) fmt. Printf ("merge T1:") treeprint (T1) fmt. Println () fmt. Printf ("Merge T2:") treeprint (T2) fmt. Println () Ret: = mergetrees (T1, t2) OK: = Treeequal (T3, ret) fmt. Printf ("merge T3:") treeprint (T1) fmt. Println () fmt. Printf ("T1:%+v, T2:%+v, t3:%+v\n", T1, T2, T3) if!ok {T.errorf ("fail, ret. Val want%+v, get%+v\n ", T3, ret)} else {T.LOGF (" Pass ")}}

C language version:

/** * Definition for a binary tree node. * struct TreeNode { *     int val; *     struct TreeNode *left; *     struct TreeNode *right; * }; */struct TreeNode* mergeTrees(struct TreeNode* t1, struct TreeNode* t2) {    if (t1 && t2) {    struct TreeNode *node = (struct TreeNode *)malloc(sizeof(struct TreeNode));    node->val = t1->val + t2->val;    node->left = mergeTrees(t1 ? t1->left : NULL, t2 ? t2->left : NULL);    node->right = mergeTrees(t1 ? t1->right : NULL, t2 ? t2->right : NULL);    return node;    }    return t1 ? t1 : t2;}

C + + Edition

/** * Definition for a binary tree node. * struct TreeNode { *     int val; *     TreeNode *left; *     TreeNode *right; *     TreeNode(int x) : val(x), left(NULL), right(NULL) {} * }; */class Solution {public:    TreeNode* mergeTrees(TreeNode* t1, TreeNode* t2) {        if (t1 && t2) {            TreeNode *node = new TreeNode(t1->val + t2->val);            node->left = mergeTrees(t1 ? t1->left : nullptr, t2 ? t2->left : nullptr);            node->right = mergeTrees(t1 ? t1->right : nullptr, t2 ? t2->right : nullptr);            return node;        }        return t1 ? t1 : t2;    }};

Java Edition:

/** * Definition for a binary tree node. * public class TreeNode { *     int val; *     TreeNode left; *     TreeNode right; *     TreeNode(int x) { val = x; } * } */public class Solution {    public TreeNode mergeTrees(TreeNode t1, TreeNode t2) {        if (t1 == null) return t2;        if (t2 == null) return t1;        int value = (t1 == null ? 0 : t1.val) + (t2 == null ? 0 : t2.val);        TreeNode node = new TreeNode(value);        node.left = mergeTrees(t1 == null ? null : t1.left, t2 == null ? null : t2.left);        node.right = mergeTrees(t1 == null ? null : t1.right, t2 == null ? null : t2.right);        return node;    }}

Link:

1. Http://www.jianshu.com/p/fc41005c1e83
2. https://leetcode.com/problems/merge-two-binary-trees/description/