二叉树深度：

#include <iostream>
#include <vector>
#include <cmath>
#include <sstream>using namespace std;struct TreeNode {int val;TreeNode* left;TreeNode* right;TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
};// 创建二叉树
TreeNode* createTree(const vector<string>& nodes, int index) {if (index >= nodes.size() || nodes[index] == "null") {return nullptr;}int val = stoi(nodes[index]);TreeNode* root = new TreeNode(val);root->left = createTree(nodes, 2 * index + 1);root->right = createTree(nodes, 2 * index + 2);return root;
}// 计算树的高度
int getHeight(TreeNode* root) {if (root == nullptr) {return 0;}int leftHeight = getHeight(root->left);int rightHeight = getHeight(root->right);return 1 + max(leftHeight, rightHeight);
}// 判断是否是平衡二叉树
bool isBalanced(TreeNode* root) {if (root == nullptr) {return true;}int leftHeight = getHeight(root->left);int rightHeight = getHeight(root->right);if (abs(leftHeight - rightHeight) <= 1 && isBalanced(root->left) && isBalanced(root->right)) {return true;}return false;
}int main() {freopen("in.txt","r",stdin);freopen("out.txt","w",stdout);string input;getline(cin, input);stringstream ss(input);vector<string> nodes;string node;while (ss >> node) {nodes.push_back(node);}TreeNode* root = createTree(nodes, 0);bool balanced = isBalanced(root);if (balanced) {cout << "True" << endl;}else {cout << "False" << endl;}return 0;
}

【问题描述】

        给定一个字符串，请将字符串里的字符按照出现的频率降序排列。例如，输入"tree"，输出结果为"eert"。输入"Aabb"，输出结果为"bbAa"。要求设计满足题目条件的如下函数：

class Solution {
public:string frequencySort(string s){  …  }
};

【输入形式】

      一个字符串。其中包括键盘上的所有可打印字符，比如空格、大小写字母、数字、标点符号等。

【输出形式】

      按字符出现频度由高到低的顺序排列的字符串。若字符出现的频度一样，则按ASCII码表中的顺序进行排列。

【样例输入】

tree

【样例输出】

        eert

【样例说明】

      b在原字符串中出现的频度最高，因此排列在最前面，字符r和t出现的频度一样，则按ASCII码表中的顺序进行排列。测试数据存放在in.txt文件中。

#include <iostream>
#include <string>
#include <unordered_map>
#include <algorithm>using namespace std;class Solution {
public:string frequencySort(string s) {unordered_map<char, int> freqMap;// 统计字符出现的频率for (char c : s) {freqMap[c]++;}// 按字符频率降序排序sort(s.begin(), s.end(), [&](char a, char b) {if (freqMap[a] != freqMap[b]) {return freqMap[a] > freqMap[b];} else {return a < b;}});return s;}
};int main() {string input;cin >> input;Solution solution;string output = solution.frequencySort(input);cout << output << endl;return 0;
}

#include <iostream>
#include <string>
#include <algorithm>
#include <vector>using namespace std;struct CharFrequency {char character;int frequency;
};class Solution {
public:static bool compare(const CharFrequency& a, const CharFrequency& b) {if (a.frequency != b.frequency) {return a.frequency > b.frequency;} else {return a.character < b.character;}}string frequencySort(string s) {vector<CharFrequency> freqList(128, {0, 0});// 统计字符出现的频率for (char c : s) {freqList[c].character = c;freqList[c].frequency++;}// 按字符频率降序排序sort(freqList.begin(), freqList.end(), compare);string result;for (const CharFrequency& cf : freqList) {result += string(cf.frequency, cf.character);}return result;}
};int main() {string input;cin >> input;Solution solution;string output = solution.frequencySort(input);cout << output << endl;return 0;
}

#include <iostream>
#include <string>
#include <algorithm>
#include <queue>
using namespace std;struct Node
{char ch;int n;Node(char ch) : ch(ch), n(0) {}Node() : ch(' '), n(0) {}
};bool compare(const Node& a, const Node& b)
{if (a.n != b.n)return a.n > b.n;return a.ch < b.ch;
}string frequencySort(string str)
{vector<Node> freqList(128, Node());// 统计字符出现的频率for (char ch : str){freqList[ch].ch = ch;freqList[ch].n++;}// 按字符频率降序排序sort(freqList.begin(), freqList.end(), compare);string result;for (const Node& node : freqList){result += string(node.n, node.ch);}return result;
}int main()
{string str;cin >> str;string output = frequencySort(str);cout << output << endl;return 0;
}