LeetCode 111. 二叉树的最小深度 简单

我的解题

BFS

#include <bits/stdc++.h>
using namespace std;
/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */

struct TreeNode
{
    int val;
    TreeNode *left;
    TreeNode *right;
    TreeNode() :
                    val(0), left(nullptr), right(nullptr)
    {
    }
    TreeNode(int x) :
                    val(x), left(nullptr), right(nullptr)
    {
    }
    TreeNode(int x, TreeNode *left, TreeNode *right) :
                    val(x), left(left), right(right)
    {
    }
};

class Solution
{
public:
    int minDepth(TreeNode *root)
    {
        if (root == nullptr)
        {
            return 0;
        }
        queue<TreeNode*> q;
        q.push(root);
        int depth = 1;
        while (!q.empty())
        {
            // 按层来进行处理
            int sz = q.size(); //当前层中节点的个数
            for (int i = 0; i < sz; ++i) //
            {
                TreeNode *n = q.front();
                q.pop();                
                if (n->left == nullptr && n->right == nullptr)
                {
                    return depth;
                }
                if (n->left)
                {
                    q.push(n->left);
                }
                if (n->right)
                {
                    q.push(n->right);

                }

            }
            ++depth;
        }

        return depth;
    }
};

// Driver code
int main()
{

    Solution solu;
    vector<int> nums = { 1, 3, 5, 4, 7 };
    return 0;
}
// g++ test.cpp --std=c++11 -pedantic -Wall -Wextra

DFS

#include <bits/stdc++.h>
using namespace std;
/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */

struct TreeNode
{
    int val;
    TreeNode *left;
    TreeNode *right;
    TreeNode() :
                    val(0), left(nullptr), right(nullptr)
    {
    }
    TreeNode(int x) :
                    val(x), left(nullptr), right(nullptr)
    {
    }
    TreeNode(int x, TreeNode *left, TreeNode *right) :
                    val(x), left(left), right(right)
    {
    }
};

class Solution
{
public:
    int minDepth(TreeNode *root)
    {
        if (root == nullptr)
        {
            return 0;
        }
        if (root->left == nullptr && root->right == nullptr)
        {
            return 1;
        }
        int min_depth = INT_MAX;
        if (root->left)
        {
            min_depth = min(min_depth, minDepth(root->left));
        }
        if (root->right)
        {
            min_depth = min(min_depth, minDepth(root->right));
        }
        return min_depth + 1;
    }
};

// Driver code
int main()
{

    Solution solu;
    vector<int> nums = { 1, 3, 5, 4, 7 };
    return 0;
}
// g++ test.cpp --std=c++11 -pedantic -Wall -Wextra

官方解题

DFS

BFS

#include <bits/stdc++.h>
using namespace std;
/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */

struct TreeNode
{
    int val;
    TreeNode *left;
    TreeNode *right;
    TreeNode() :
                    val(0), left(nullptr), right(nullptr)
    {
    }
    TreeNode(int x) :
                    val(x), left(nullptr), right(nullptr)
    {
    }
    TreeNode(int x, TreeNode *left, TreeNode *right) :
                    val(x), left(left), right(right)
    {
    }
};

class Solution
{
public:
    int minDepth(TreeNode *root)
    {
        if (root == nullptr)
        {
            return 0;
        }

        queue<pair<TreeNode*, int> > que;
        que.emplace(root, 1);
        while (!que.empty())
        {
            TreeNode *node = que.front().first;
            int depth = que.front().second;
            que.pop();
            if (node->left == nullptr && node->right == nullptr)
            {
                return depth;
            }
            if (node->left != nullptr)
            {
                que.emplace(node->left, depth + 1);
            }
            if (node->right != nullptr)
            {
                que.emplace(node->right, depth + 1);
            }
        }

        return 0;
    }
};

// Driver code
int main()
{

    Solution solu;
    vector<int> nums = { 1, 3, 5, 4, 7 };
    return 0;
}
// g++ test.cpp --std=c++11 -pedantic -Wall -Wextra