164 lines
4 KiB
C++
164 lines
4 KiB
C++
#include "cal.h"
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QString inToPost(QString infix) {
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std::stack<char> stack;
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char current = 0; //读入的字符
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QString postfix; //写入后缀表达式的字符串
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std::map<char, int> priority; //运算符号优先级表
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priority['+'] = 0;
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priority['-'] = 0;
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priority['*'] = 1;
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priority['/'] = 1;
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priority['^'] = 2;
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for (int i = 0; i < infix.length(); ++i) //逐个读取中缀表达式字符串中的字符
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{
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current = infix[i].toLatin1();
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if (isdigit(current)) //如果是数字直接输出
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{
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postfix.push_back(current);
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continue;
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}
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switch (current) {
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case '+':
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case '-':
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case '*':
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case '/':
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case '^':
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// postfix.push_back('#');
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if (i >
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0) //如果运算符的前一项不是右括号则说明前一个数字输入完毕，用#标识前面几个字符组成一个数字
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{
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if (infix[i - 1] != ')')
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postfix.push_back('#');
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/*if(infix[i-1].isDigit())
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postfix.push_back('#');
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else
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throw "expression is illegality";*/
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} else
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postfix.push_back('#');
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if (!stack
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.empty()) //比较目前符号与栈顶符号优先级，低于则出栈，并输出字符串
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{
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char tempTop = stack.top();
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while (tempTop != '(' && priority[current] <= priority[tempTop]) {
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stack.pop();
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postfix.push_back(tempTop);
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if (stack.empty())
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break;
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tempTop = stack.top();
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}
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}
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stack.push(
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current); //符号全部出栈或者遇到了'('或者大于栈顶符号的优先级，将新符号压入栈中
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break;
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case '.':
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postfix.push_back(current);
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break;
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case '%':
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postfix.push_back(current);
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break;
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case '(':
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stack.push(current); //左括号直接入栈
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break;
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case ')':
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postfix.push_back('#'); //右括号说明前方数字输入完成，标识一下
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char tempTop;
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tempTop = stack.top();
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while (tempTop != '(') //直到栈顶元素是左括号才停止循环
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{
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stack.pop();
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postfix.push_back(tempTop);
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tempTop = stack.top();
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}
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stack.pop();
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break;
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default:
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throw "expression has illegality character";
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break;
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}
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}
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if (infix[infix.size() - 1] != ')') {
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if (infix[infix.size() - 1].isDigit())
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postfix.push_back('#');
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else
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throw "expression is illegality";
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}
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while (!stack.empty()) {
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char tempOut = stack.top();
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stack.pop();
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postfix.push_back(tempOut);
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}
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return postfix;
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}
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double compute(QString s) {
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std::stack<double> stack;
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QString str;
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double curr;
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double temNum1;
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double temNum2;
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for (auto i = s.begin(); i != s.end(); i++) {
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if ((*i).isDigit()) {
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str.push_back(*i);
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continue;
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}
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switch ((*i).toLatin1()) {
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case '+':
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temNum1 = stack.top();
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stack.pop();
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temNum2 = stack.top();
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stack.pop();
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stack.push(temNum2 + temNum1);
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break;
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case '-':
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temNum1 = stack.top();
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stack.pop();
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temNum2 = stack.top();
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stack.pop();
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stack.push(temNum2 - temNum1);
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break;
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case '*':
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temNum1 = stack.top();
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stack.pop();
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temNum2 = stack.top();
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stack.pop();
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stack.push(temNum2 * temNum1);
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break;
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case '/':
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temNum1 = stack.top();
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stack.pop();
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temNum2 = stack.top();
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stack.pop();
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stack.push(temNum2 / temNum1);
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break;
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case '^':
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temNum1 = stack.top();
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stack.pop();
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temNum2 = stack.top();
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stack.pop();
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stack.push(pow(temNum2, temNum1));
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break;
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case '.':
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str.push_back(*i);
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break;
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case '#':
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curr = str.toDouble(); //字符串转换为浮点型
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str.clear();
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stack.push(curr);
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break;
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case '%':
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curr = stack.top();
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stack.pop();
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curr *= 0.01;
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stack.push(curr);
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break;
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default:
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throw "expression has illegality character";
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break;
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}
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}
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curr = stack.top();
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return curr;
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}
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