Question

Hello, please correct the following C++ CODE it is not working on visual studio: (I WILL RATE, NO INCOMPLETE OR WRONG SOLUTIONS PLEASE)

// CPP program to evaluate a given
// expression where tokens are
// separated by space.
#include
using namespace std;

// Function to find precedence of
// operators.
int precedence(char op){
if(op == '+'||op == '-')
return 1;
if(op == '*'||op == '/')
return 2;
return 0;
}

// Function to perform arithmetic operations.
int applyOp(int a, int b, char op){
switch(op){
case '+': return a + b;
case '-': return a - b;
case '*': return a * b;
}
}

// Function that returns value of
// expression after evaluation.
int evaluate(string tokens){
int i;
  
// stack to store integer values.
stack values;
  
// stack to store operators.
stack ops;
  
for(i = 0; i < tokens.length(); i++){
  
// Current token is a whitespace,
// skip it.
if(tokens[i] == ' ')
continue;
  
// Current token is an opening
// brace, push it to 'ops'
else if(tokens[i] == '('){
ops.push(tokens[i]);
}
  
// Current token is a number, push
// it to stack for numbers.
else if(isdigit(tokens[i])){
int val = 0;
  
// There may be more than one
// digits in number.
while(i < tokens.length() &&
isdigit(tokens[i]))
{
val = (val*10) + (tokens[i]-'0');
i++;
}
  
values.push(val);
}
  
// Closing brace encountered, solve
// entire brace.
else if(tokens[i] == ')')
{
while(!ops.empty() && ops.top() != '(')
{
int val2 = values.top();
values.pop();
  
int val1 = values.top();
values.pop();
  
char op = ops.top();
ops.pop();
  
values.push(applyOp(val1, val2, op));
}
  
// pop opening brace.
ops.pop();
}
  
// Current token is an operator.
else
{
// While top of 'ops' has same or greater
// precedence to current token, which
// is an operator. Apply operator on top
// of 'ops' to top two elements in values stack.
while(!ops.empty() && precedence(ops.top())
>= precedence(tokens[i])){
int val2 = values.top();
values.pop();
  
int val1 = values.top();
values.pop();
  
char op = ops.top();
ops.pop();
  
values.push(applyOp(val1, val2, op));
}
  
// Push current token to 'ops'.
ops.push(tokens[i]);
}
}
  
// Entire expression has been parsed at this
// point, apply remaining ops to remaining
// values.
while(!ops.empty()){
int val2 = values.top();
values.pop();
  
int val1 = values.top();
values.pop();
  
char op = ops.top();
ops.pop();
  
values.push(applyOp(val1, val2, op));
}
  
// Top of 'values' contains result, return it.
return (values.top())%3;
}

int main() {
cout << evaluate("10 + 2 * 6") << "\n";
cout << evaluate("100 * 2 + 12") << "\n";
cout << evaluate("100 * ( 2 + 12 )") << "\n";
cout << evaluate("100 * ( 2 + 12 ) / 14");
return 0;
}

THANK YOU.

Answer 1

main.cpp

#include <bits/stdc++.h>

using namespace std;

// Function to find precedence of

// operators.

int precedence(char op){

if(op == '+'||op == '-')

return 1;

if(op == '*'||op == '/')

return 2;

return 0;

}

// Function to perform arithmetic operations.

int applyOp(int a, int b, char op){

switch(op){

case '+': return a + b;

case '-': return a - b;

case '*': return a * b;

case '/': return a / b;

}

}

// Function that returns value of

// expression after evaluation.

int evaluate(string tokens){

int i;

// stack to store integer values.

stack <int> values;

// stack to store operators.

stack <char> ops;

for(i = 0; i < tokens.length(); i++){

// Current token is a whitespace,

// skip it.

if(tokens[i] == ' ')

continue;

// Current token is an opening

// brace, push it to 'ops'

else if(tokens[i] == '('){

ops.push(tokens[i]);

}

// Current token is a number, push

// it to stack for numbers.

else if(isdigit(tokens[i])){

int val = 0;

// There may be more than one

// digits in number.

while(i < tokens.length() &&

isdigit(tokens[i]))

{

val = (val*10) + (tokens[i]-'0');

i++;

}

values.push(val);

}

// Closing brace encountered, solve

// entire brace.

else if(tokens[i] == ')')

{

while(!ops.empty() && ops.top() != '(')

{

int val2 = values.top();

values.pop();

int val1 = values.top();

values.pop();

char op = ops.top();

ops.pop();

values.push(applyOp(val1, val2, op));

}

// pop opening brace.

ops.pop();

}

// Current token is an operator.

else

{

// While top of 'ops' has same or greater

// precedence to current token, which

// is an operator. Apply operator on top

// of 'ops' to top two elements in values stack.

while(!ops.empty() && precedence(ops.top())

>= precedence(tokens[i])){

int val2 = values.top();

values.pop();

int val1 = values.top();

values.pop();

char op = ops.top();

ops.pop();

values.push(applyOp(val1, val2, op));

}

// Push current token to 'ops'.

ops.push(tokens[i]);

}

}

// Entire expression has been parsed at this

// point, apply remaining ops to remaining

// values.

while(!ops.empty()){

int val2 = values.top();

values.pop();

int val1 = values.top();

values.pop();

char op = ops.top();

ops.pop();

values.push(applyOp(val1, val2, op));

}

// Top of 'values' contains result, return it.

return values.top();

}

int main() {

cout<<endl;

cout << evaluate("10 + 2 * 6") << "\n";

cout << evaluate("100 * 2 + 12") << "\n";

cout << evaluate("100 * ( 2 + 12 )") << "\n";

cout << evaluate("100 * ( 2 + 12 ) / 14");

return 0;

}

Output: