/****************************************** Author: Nautash Ahmad Created: 10th November, 2018 ------------------------------------------- Description: A simple calculator that performs the basic operations. ------------------------------------------- Note: Currently supported operators are: 1) Exponential (^) 2) Multiplication (*) 3) Division (/) 4) Addition (+) 5) Subtraction (-) All operators should be binary, means having two operands. 1) 2^3 = 8 2) 3*6 = 18 3) 4/2 = 2 4) 20+100 = 120 5) 100-80 = 20 Below are sample inputs: 1) 4+2*8 2) 14+20-80/2 3) 4^2+20/5+4*7-1 You can put spaces between operators and operands for readibilty of an expression. Only contants operands can be used. Brackets/Paranthesis are not supported. That will be added soon. Dividing by Zero error is not supported right now. I'll add it soon. If you find any bugs, let me know. Happy to hear if you have any suggestions. ******************************************/ #include #include #include #include using namespace std; string InfixToPostfix(string exp); bool GreaterPreceedence(char topOpr, char expOpr); bool EqualPreceedence(char topOpr, char expOpr); bool IsOperand(char ch); bool IsOperator(char ch); int SolveExpression(string postfix); int SolveOpr(int leftOpr, int rightOpr, char optr); int main() { string exp; getline(cin, exp); cout << "Infix expression: " << exp << endl; string postfix = InfixToPostfix(exp); cout << "Postfix expression: " << postfix << endl; int ans = SolveExpression(postfix); cout << exp << " = " << ans << endl; return 0; } string InfixToPostfix(string exp) { string postfix = "\0"; stack S; for(int i = 0; i < exp.size(); i++) { if(IsOperand(exp[i])) { postfix += exp[i]; if(!IsOperand(exp[i+1])) postfix += " "; } else { if(IsOperator(exp[i])) { if(S.empty()) S.push(exp[i]); else { if(GreaterPreceedence(S.top(), exp[i])) { postfix += S.top(); postfix += " "; S.pop(); if(EqualPreceedence(S.top(), exp[i])) { postfix += S.top(); postfix += " "; S.pop(); } S.push(exp[i]); } else if(EqualPreceedence(S.top(), exp[i])) { postfix += S.top(); postfix += " "; S.pop(); S.push(exp[i]); } else S.push(exp[i]); } } } } while(!S.empty()) { postfix += S.top(); postfix += " "; S.pop(); } return postfix; } bool GreaterPreceedence(char topOpr, char expOpr) { if((topOpr == '^') && (expOpr == '*' || expOpr == '/' || expOpr == '+' || expOpr == '-')) return true; else if((topOpr == '*' || topOpr == '/') && (expOpr == '+' || expOpr == '-')) return true; else return false; } bool EqualPreceedence(char topOpr, char expOpr) { if((topOpr == '+' && expOpr == '-') || (topOpr == '-' && expOpr == '+')) return true; else if((topOpr == '*' && expOpr == '/') || (topOpr == '/' && expOpr == '*')) return true; else return false; } bool IsOperand(char ch) { if(ch >= 48 && ch < 58) return true; else return false; } bool IsOperator(char ch) { if(ch == '*' || ch == '/' || ch == '+' || ch == '-' || ch == '^') return true; else return false; } int SolveExpression(string postfix) { stack opr; int ans = 0, num = 0; for(int i = 0; i < postfix.size(); i++) { if(IsOperand(postfix[i])) { if(IsOperand(postfix[i+1])) { int digit = postfix[i] - '0'; num = (num * 10) + digit; } else if(postfix[i+1] == ' ') { int digit = postfix[i] - '0'; num = (num * 10) + digit; opr.push(num); } else { num = postfix[i] - '0'; opr.push(num); } } else if(IsOperator(postfix[i])) { int rightOpr = opr.top(); opr.pop(); int leftOpr = opr.top(); opr.pop(); ans = SolveOpr(leftOpr, rightOpr, postfix[i]); if(i != (postfix.size() - 1)) opr.push(ans); } else num = 0; } return ans; } int SolveOpr(int leftOpr, int rightOpr, char optr) { switch(optr) { case '*': { return leftOpr * rightOpr; } case '/': { return leftOpr / rightOpr; } case '+': { return leftOpr + rightOpr; } case '-': { return leftOpr - rightOpr; } case '^': { return pow(leftOpr, rightOpr); } } }

Expression Solver v1.0