C++實現四則運算器(帶括號)
阿新 • • 發佈：2020-08-06
基本分析可以看另一篇文章C++實現四則運算器(無括號)
棧的實現
//stack.h #ifndef STACK_H #define STACK_H #include<iostream> class stack_int { private: int* bottom; //棧底 int* top; //棧頂 unsigned int capacity;//棧容量 unsigned int size; //棧大小 public: stack_int() :bottom(new int[11]), top(bottom), capacity(10), size(0) {}; stack_int(unsigned int capacity) :bottom(new int[capacity+1]),top(bottom), capacity(capacity),size(0){}; int operator[](unsigned int i) const { return *(bottom + i); } bool isEmpty()const { return bottom == top; } bool isFull()const { return size == capacity-1; } unsigned int getsize()const { return size; } unsigned int getcapacity()const { return capacity; } int gettop()const { if (!isEmpty()) return *(top - 1); else return -1; } void settop(int i) { if (!isEmpty()) { *(top - 1) = i; } } void push(int i) { if ((top - bottom)<capacity) { *top = i; top++; size++; } else { std::cout << "stack full!" << std::endl; stack_expansion(); push(i); } } int pop(int &val) {//返回值為1則棧未空，返回值為0則棧已空無法出棧 if (top > bottom) { top--; size--; val = *top; return 1; } else { std::cout << "stack empty!" << std::endl; return NULL; } } private: void stack_expansion() {//棧擴容 std::cout << "正在擴容中..." << std::endl; int newcapacity = 2 * capacity + 1; int* newbottom = new int[newcapacity + 1]; int* newtop = newbottom; for (int i = 0; i < size; ++i) { *newtop = *bottom; newtop++; bottom++; } bottom = newbottom; top = newtop; capacity = newcapacity; } }; #endif
主程式
//Main.c #include"stack.h" #include<iostream> using namespace std; bool is_digit(char i) {//是數字 if (i == '1' || i == '2' || i == '3' || i == '4' || i == '5' || i == '6' || i == '7' || i == '8' || i == '9' || i == '0') return true; else return false; } bool is_operator(char i) {//是運算子 if (i == '+' || i == '-' || i == '*' || i == '/' || i == '(' || i == ')'||i=='=') return true; else return false; } bool get_priority(char pre,char cur) {//獲取兩個符號間的優先順序,pre為靠前的字元，cur為靠後的字元 if ((pre == '+' || pre == '-') && (cur == '*' || cur == '/')) return false; else if (pre == '(' || cur == '(') return false; else return true; } int do_operation(int lnum, char ope, int rnum) { if (ope == '+') return lnum + rnum; if (ope == '-') return lnum - rnum; if (ope == '*') return lnum * rnum; if (ope == '/') return lnum / rnum; } /* 1+2*3= 1*(2+1*(3+5)+4*3)= 先乘除，後加減，有括號先算括號內的 1+5*4-345+36/6*4+145*4*5-52= */ void do_arithmetic() { stack_int s; stack_int num_stack;//資料棧 stack_int ope_stack;//符號棧 char current_char; current_char = getchar(); bool overflag = false;//結束標誌 bool errorflag = false;//出錯標誌 while (overflag != true) {//未遇到=號時不斷進行四則運算 if (is_digit(current_char)) {//遇到數字符號則將完整的數解析出來並保存於棧中 int num = 0; num = current_char - '0';//符號轉數字 current_char = getchar();//獲取下一個字元 while (is_digit(current_char)) { num = num * 10 + (current_char - '0'); current_char = getchar(); } num_stack.push(num); //cout <<"the number is " <<num << endl; } if (current_char == ' '||current_char=='\n') {//空格或換行則繼續 current_char = getchar(); continue; } if (is_operator(current_char)) {//遇到運算子則將運算子保存於運算子棧中 int ope = '?'; //如果當前符號棧非空，則不斷根據優先順序決定是否進行一次運算 while ((!ope_stack.isEmpty()) && (get_priority((char)ope_stack.gettop(), current_char))) {//如果前一個運算子優先順序更高 ope_stack.pop(ope); //cout << "找到了前一個運算子為: " << (char)ope << endl; int lnum, rnum; //符號棧非空時，資料棧應該至少有兩個數，否則出錯 if (num_stack.isEmpty()) { cout << "error: 資料棧缺失兩個元素，解析失敗！" << endl; errorflag = true; overflag = true; break; } num_stack.pop(rnum); if (num_stack.isEmpty()) { cout << "error: 資料棧缺失一個元素，解析失敗！" << endl; errorflag = true; overflag = true; break; } num_stack.pop(lnum); lnum = do_operation(lnum, (char)ope, rnum);//進行運算 num_stack.push(lnum); } if (current_char == '=') {//如果解析到=號了,解析完成 if (!ope_stack.isEmpty()) { errorflag = true; cout << "error: 缺失)" << endl; } overflag = true; break; } ope_stack.push(current_char); if (current_char == ')') {//右括號則出棧兩次，將右括號和匹配的左括號出棧 ope_stack.pop(ope); if (ope_stack.isEmpty()) { cout << "error: 沒有與)相匹配的(" << endl; errorflag = true; overflag = true; break; } ope_stack.pop(ope); } current_char = getchar(); } } //for (int i = 0; i < num_stack.getsize(); ++i) // cout << num_stack[i] << "\t"; //cout << endl; //for (int i = 0; i < ope_stack.getsize(); ++i) // cout << (char)ope_stack[i] << "\t"; if (!errorflag) cout << num_stack.gettop() << endl; } int main() { cout << " ______________" << endl; cout << "|整數四則運算器|" << endl; cout << " --------------" << endl; cout << "功能介紹：進行整數表示式的四則運算" << endl; cout << "可以使用的運算子:+ - * /" << endl; cout << "使用方式:輸入以=結尾的算數運算表示式,回車後即可得到運算結果" << endl; cout << endl; //2432+5423-534*42= while (true) { cout << "____________________" << endl; cout << "--------------------" << endl; cout << "> "; do_arithmetic(); } return 0; }
程式大部分與不帶括號版本很相似，主要更改了兩個方面：
1.對於左括號，令左括號左邊運算子優先順序低於左括號，右邊運算子優先順序高於左括號(即，只要含有左括號的比較結果均為無法進行運算，函式get_priority返回值永遠為false)。
2.對於右括號，令右括號左邊的運算子(除左括號外)優先順序均高於右括號，並且當右括號左邊的符號為左括號時，兩個括號相抵消，左括號退棧。
遇到右括號時，兩括號內的+-*/運算全部可以進行，直到符號棧棧頂為左括號。