program for user algebra

Hello....
I am trying this from 4 days but i cannot be able to get the correct result......the problem is....
The user enters the algebraic expression with +,-,(,),/,a,b,c
and so the values of a,b,c...the program must show him the result of the expression....for example, Enter your expression a+(b/c)+ac
enter the values for a
4
enter the values for b
25
enter the values for c
5
result=29

please give me the code
#include<stdio.h> #include<conio.h> void main(){ int a,b,c,i,j,r=1; char ch[10]; clrscr(); printf("enter your expression\n"); gets(ch); i=0; while(i<=strlen(ch)-1) { if(ch[i]=='a') { printf("enter the a value"); scanf("%d",&a); } else if(ch[i]=='b') { printf("enter b value"); scanf("%d",&b); } else if(ch[i]=='c') { printf("enter c value"); } if(ch[i]=='+'||ch[i]=='-'||ch[i]=='('||ch[i]==')'||ch[i]=='/') { i++; } } j=strlen(ch)-1; while(/* DONT KNOW WHAT CONDITION I MUST GIVE */) { r=ch[j]*r; j--; } }
upto here i've written and in the second while loop i am getting a problem as the calculation is performing for each j--; suppose if the array is 4 + ( 25 / 5 ) + 4 5 as j=strlen(ch)-1; therefore ch[j]=5 and r is r=5*1 next j decrements and ch[j]=4 and r becomes 5*4 20 and so on................
but, the calculation must be performed according to the operator precedence i mean division operator has more prior then others and my result is getting wrong........

- shravanreddynallabolu December 19, 2013 | Flag |

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function solve(exp)
{
    
    var rank = {'+':1, '-':1, '/':2, '*':2};
    var func = {
        '+': function(e1, e2) {
            return parseFloat(e1)+parseFloat(e2);
        },
        '-': function(e1, e2) {
            return parseFloat(e1)-parseFloat(e2);
        },
        '/': function(e1, e2) {
            return parseFloat(e1)/parseFloat(e2);
         },
        '*': function(e1, e2) {
            return parseFloat(e1)*parseFloat(e2);
        }
    };
   
                            
    var stack=new Array();
    var fexp = new Array();
    for(var i = 0; i < exp.length; i++)
    {
        if(IsNumeric(exp[i]))
        {
            fexp.push(exp[i]);
        }
        else
        {
            console.log('rank: ' + exp[i] + ' ' + rank[exp[i]]);
            if(stack.length == 0 || rank[exp[i]] > rank[stack[stack.length - 1]])
                stack.push(exp[i]);
            else
            {
                do
                {
                    fexp.push(stack.pop());
                }
                while(rank[exp[i]] <= rank[stack[stack.length - 1]]);
                
                stack.push(exp[i]);
            }
        }
    }
    
    while(stack.length != 0)
        fexp.push(stack.pop());
    
    console.log(fexp);
    for(var i = 0; i< fexp.length; i++)
    {
        if(IsNumeric(fexp[i]))
        {
            stack.push(fexp[i]);
        }
        else
        {
            var e1 = stack.pop();
            var e2 = stack.pop();
            console.log(fexp[i] + ': ' + [e2, e1]);
            var val = func[fexp[i]](e2, e1);
            console.log('res: ' + val); 
            stack.push(val);
        }
    }
    
    alert(stack.pop());
    
}
           
function IsNumeric(input){
    var RE = /^-{0,1}\d*\.{0,1}\d+$/;
    return (RE.test(input));
}

solve('1+8/4/2')

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