Analog calculator: evaluate an expression with addition, subtraction, multiplication, division, and parentheses

 

// Integer, add, subtract, multiply, divide, evaluate multiple parentheses, for example,-1 + (2-(3 + 4)/7) * 5, (without input check): # include <sstream> # include <iostream> # include <string> using namespace STD; int stoi (string S); string itos (INT Myint ); string scalculate (string S1, string S2, char OPR); string nobracket (string S); void main () {int N, start = 0, I; string S, S1; cout <"input the expression:" <Endl; CIN> S; // example-1 + (2-(3 + 4)/7) * 5 // processing brackets: While (start! =-1) {start =-1; n = S. length (); for (I = 0; I <n; I ++) {If (S. at (I) = '(') {start = I + 1;} else if (S. at (I) = ') {S1 = nobracket (S. substr (start, I-Start); // process the subexpression S = s without parentheses. substr (0, start-1) + S1 + S. substr (I + 1); // Replace the values in the brackets with the original brackets and their content. // cout <"s =" <S <Endl; break ;}}} S = nobracket (s); // process the entire cout expression without parentheses <S <Endl;} string nobracket (string S) {// process the entire expression int start = 0, N, I, j, m = 0; char C; string sub without parentheses S [200]; C = S. at (0); If (C = '+') s. replace (, ""); // if the expression starts with a positive sign, remove it else if (C = '-') s. replace (, "_"); // replace N = s with an underscore if the expression starts with a negative sign. length (); for (I = 0; I <n; I ++) {c = S. at (I); If (C = '+' | C = '-' | C = '*' | C = '/') {Subs [M ++] = S. substr (start, I-Start); // place each number and operator in the subs [] Unit of the array. Subs [M ++] = C; start = I + 1 ;}} subs [m] = S. substr (start); I = 0; while (I <m) {c = Subs [I]. at (0); If (C = '*' | C = '/') {// first multiply the subs [I-1] = Scalculate (subs [I-1], subs [I + 1], c); For (j = I; j <m-1; j ++) subs [J] = Subs [J + 2]; m-= 2;} else I ++;} for (I = 1; I <m; I = I + 2) {// add or subtract subs [0] = scalculate (subs [0], subs [I + 1], subs [I]. at (0);} return subs [0];} string scalculate (string S1, string S2, char OPR) {// calculate the two strings to obtain a string if (OPR = '+') return itos (stoi (S1) + stoi (S2 )); else if (OPR = '-') return itos (stoi (S1)-stoi (S2); else if (OPR = '*') return itos (stoi (S1) * St Oi (S2); else if (OPR = '/') return itos (stoi (S1)/stoi (S2); else return "error OPR! ";} Int stoi (string s) {// convert string to int if (S. at (0) = '_') s. replace (, "-"); // restores the underline to the negative istringstream buffer (s); int Myint; buffer> Myint; return Myint;} string itos (INT Myint) {// convert int to string ostringstream buffer; buffer <Myint; return buffer. STR ();}

 

Analog calculator: evaluate an expression with addition, subtraction, multiplication, division, and parentheses