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Practical-Teaching/Professional-Comprehensive-Training-I/1.2.cpp

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+// Copyright (c) 2023 徐丞烨，王凯钦，宋析峰，杨崇新
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+#include <bits/stdc++.h>
+
+using namespace std;
+
+// 定义节点结构体
+struct Node {
+	char operato;	// 运算符
+	double operand; // 操作数
+	Node *left;		// 左子树
+	Node *right;	// 右子树
+	Node(char o = 0, double d = 0, Node *l = nullptr, Node *r = nullptr) : operato(o), operand(d), left(l), right(r) {}
+};
+
+// 定义树类型
+using Tree = Node *;
+
+// 递归构建表达式树
+Tree buildTree(stringstream &ss) {
+	string e;
+	ss >> e;
+	// 如果是加法
+	if (e == "add") {
+		Tree t = new Node('+');
+		t->left = buildTree(ss);
+		t->right = buildTree(ss);
+		return t;
+	}
+	// 如果是减法
+	else if (e == "sub") {
+		Tree t = new Node('-');
+		t->left = buildTree(ss);
+		t->right = buildTree(ss);
+		return t;
+	}
+	// 如果是乘法
+	else if (e == "muti") {
+		Tree t = new Node('*');
+		t->left = buildTree(ss);
+		t->right = buildTree(ss);
+		return t;
+	}
+	// 如果是除法
+	else if (e == "div") {
+		Tree t = new Node('/');
+		t->left = buildTree(ss);
+		t->right = buildTree(ss);
+		return t;
+	}
+	// 如果是取负
+	else if (e == "neg") {
+		double temp;
+		ss >> temp;
+		return new Node(0, -temp);
+	}
+	// 如果是平方
+	else if (e == "doubleMe") {
+		Tree t = new Node('^');
+		double temp;
+		ss >> temp;
+		t->left = new Node(0, temp);
+		t->right = new Node(0, 2);
+		return t;
+	}
+	// 如果是数字
+	else
+		return new Node(0, atof(e.c_str()));
+}
+
+// 判断节点是否为运算符
+bool isOperator(const Tree t) {
+	return t->operato != 0;
+}
+
+// 定义运算符优先级
+map<char, int> priority{ { '+', 1 }, { '-', 1 }, { '*', 2 }, { '/', 2 }, { '^', 3 } };
+
+// 判断运算符优先级是否小于等于另一个运算符
+bool lowerOrEqualPrecedence(const char op1, const char op2) {
+	return priority[op1] <= priority[op2];
+}
+
+// 输出表达式树
+void print(ostream &out, const Tree t = nullptr) {
+	if (t == nullptr)
+		return;
+	if (isOperator(t)) {
+		bool leftParen = isOperator(t->left) && lowerOrEqualPrecedence(t->left->operato, t->operato);
+		bool rightParen = isOperator(t->right) && lowerOrEqualPrecedence(t->right->operato, t->operato);
+		if (leftParen)
+			out << "(";
+		print(out, t->left);
+		if (leftParen)
+			out << ")";
+		out << ' ' << t->operato << ' ';
+		if (rightParen)
+			out << "(";
+		print(out, t->right);
+		if (rightParen)
+			out << ")";
+	}
+	else
+		out << t->operand;
+}
+
+// 计算表达式树的值
+double evaluate(const Tree t) {
+	if (t == nullptr)
+		return 0;
+	if (isOperator(t)) {
+		double left = evaluate(t->left);
+		double right = evaluate(t->right);
+		switch (t->operato) {
+		case '+':
+			return left + right;
+		case '-':
+			return left - right;
+		case '*':
+			return left * right;
+		case '/':
+			return left / right;
+		case '^':
+			return pow(left, right);
+		}
+	}
+	return t->operand;
+}
+
+int main() {
+	// 从文件中读取表达式
+	ifstream fin("E:\\OneDrive\\Code\\C++\\Professional-Comprehensive-Training-I\\question.txt");
+	// 将计算结果写入文件
+	ofstream fout("E:\\OneDrive\\Code\\C++\\Professional-Comprehensive-Training-I\\answer.txt");
+	string line;
+	while (getline(fin, line)) {
+		string temp = line;
+		// 将括号和逗号替换为空格
+		for (char &c : temp)
+			if (c == '(' || c == ')' || c == ',')
+				c = ' ';
+		// 将表达式转换为流并构建表达式树
+		stringstream ss(temp);
+		Tree t = buildTree(ss);
+		// 输出表达式和计算结果
+		print(fout, t);
+		fout << " = " << evaluate(t);
+		fout << endl;
+	}
+	// 关闭文件
+	fin.close();
+	fout.close();
+	return 0;
+}