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balanced_binary_tree.cpp
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balanced_binary_tree.cpp
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/*
* =====================================================================================
*
* Filename: balanced_binary_tree.cpp
*
* Description: 110. Balanced Binary Tree.
* Given a binary tree, determine if it is height-balanced.
*
* Version: 1.0
* Created: 04/12/19 12:42:30
* Revision: none
* Compiler: gcc
*
* Author: Zhu Xianfeng (), [email protected]
* Organization:
*
* =====================================================================================
*/
#include <algorithm>
#include <utility>
#include <vector>
#include "gmock/gmock.h"
#include "gtest/gtest.h"
struct TreeNode {
int val;
TreeNode* left;
TreeNode* right;
TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
static TreeNode* convert(const std::vector<int*>& nums, const int i = 0) {
if (i >= nums.size() || nums[i] == nullptr) {
return nullptr;
}
TreeNode* root = new TreeNode(*nums[i]);
root->left = convert(nums, 2 * i + 1);
root->right = convert(nums, 2 * i + 2);
return root;
}
};
class Solution {
public:
bool isBalanced(TreeNode* root) { return (checkHeight(root) != -1); }
private:
int checkHeight(TreeNode* node) {
if (node == nullptr) {
return 0;
}
int left = checkHeight(node->left);
if (left == -1) {
// Left subtree isn't balanced
return -1;
}
int right = checkHeight(node->right);
if (right == -1) {
// Right subtree isn't balanced
return -1;
}
if (std::abs(left - right) > 1) {
// Current tree isn't balanced
return -1;
}
// Return current tree's height
return std::max(left, right) + 1;
}
};
TEST(Solution, isBalanced) {
#define _N(x) new int(x)
std::vector<std::pair<TreeNode*, bool>> cases = {
std::make_pair(TreeNode::convert(
std::vector<int*>{_N(3), _N(9), _N(20), nullptr, nullptr, _N(15), _N(7)}),
true),
std::make_pair(TreeNode::convert(std::vector<int*>{_N(1), _N(2), _N(2), _N(3), _N(3), nullptr,
nullptr, _N(4), _N(4)}),
false),
std::make_pair(TreeNode::convert(std::vector<int*>{nullptr}), true),
};
for (auto& c : cases) {
EXPECT_EQ(Solution().isBalanced(c.first), c.second);
}
#undef _N
}