Thread: please ....i need help with this program

Originally Posted by iMalc

Ah now that code could actually do something useful. It doesn't solve the whole problem, but it does solve part of it, if you know what comes after it. However, unless you can demonstrate that you understand how that works, I'm inclined to believe that it is someone else's code.

Perhaps you could attempt to describe in your own words, the algorithm you will use to solve the problem. It doesn't matter if you get it wrong or get stuck, just give it a try and we'll give you a nudge.

You are right it’s not my code; I can’t solve it by myself….

Originally Posted by iMalc

Okay it might be easiest if we start with pinning down what it takes for the expression to be invalid.
Here are a few examples:

Code:

1 ( 2 )
+ 3
)

The first one is invalid because a bracket should not come directly after a number
The second one is invalid because a plus sign must not be the first thing in the expression.
The Third one is invalid because an expression must not start with a close bracket, or more accurately, the close bracket does not have a corresponding open bracket before it.
See how many more you can come up with.
Then once you think you've got all the rules about when something is invalid, then you've got a good idea on what it takes for an expression to be valid, and after that you might be able to work out pseudocode for solving this and then onto the real code.

One thing though, do you know all of the possible things that can be in an expression? I mean it can have plus, minus, multiply and divide, but can it also have thing like ^ which means to-the-power-of? If you aren't sure, then just assume it only has +, -, *, /, (, ).

k what else...?

Originally Posted by creeping death

hi, i think the OP just wants to check if the brackets are correct and balanced out...but anyway...please ignore me and continue...you're doing an awesome thing btw.

whyyyyyyyyy? please i need your help

How about putting the expression, into a string of char's:

Code:

Pseudocode:
char exp[50] = { '\0' };

fgets() can get the expression from the user, and put it into the exp array

then have 2 int variables to count up the left and right tally of brackets:
int left, right, noGood;

then we can scan the exp array, char by char:
left = right = noGood = 0;
for(i = 0; exp[i] != '\0'; i++)  {
   if(exp[i] == '(')
      left++;
   else if(exp[i] == ')')
      right++;


   //there can't be more right brackets then left brackets in the expression, at any time
   if(right > left)
      noGood = 1;
     
}

Now if left == right and noGood still equals 0, it's OK.

So print that message

Note that this is pseudocode, not ready-to-run code.

Originally Posted by iMalc

Okay, now start with a basic Hello World program, and add in something to read in the expression from the user. You'll need something like fgets and sscanf and an array of chars, though there is certainly more than one way of doing it.
See if you can write a program that reads in a sentence and writes it out back to you again.

#include<stdio.h>
#include<conio.h>
void main()
{
int x,y,sum;
printf("please enter your value");
scanf("%d%d",&x,&y);
sum=x+y;
printf("the answer is %d ",z);
getch();
}


loool

you can't use z, since you didn't declare it. sum is what you want, isn't it?

Please use code tags around your code. Click on the # sign after you highlight your code, to do that.

should it fix it or only detect if there its right or not ?
i coded a fix program for it

Code:

#include <stdio.h>
void string_fixer(char *buffer)
{
    int i;//loop counter
    for(i=0;buffer[i]!=0;i++){
             if(buffer[0]=='('){
                   
             if(buffer[i]=='/'){
                buffer[i-2]=')';
                }
           }
    }
}
int main(void)
{
    char buffer[100];
    double x;//for atoi
    sprintf(buffer,"( 3 * 4 + 2 ( / (8-2)");
    string_fixer(buffer);
    puts(buffer);
    return getchar();
}

you should ident your code lil bit and put instead of z put num coz thats ur equation whish sum = x+y

here you go~~

code not tested!!

Code:

main(){

	char *input="(2+3)+((4-6)";
	int flag=0;

	while(*input){
		if(*input=='('){
			flag++;
		}else if(*input==')'){
			flag--;
		}
		if(flag<0){
			printf("Incorrect brackets starting at: %s\n",input);
			exit(0);
		}
		*input++;	
	}

	if(flag!=0){
			printf("Probably %d closing bracket(s) missing brackets\n",flag);
	}else{
		printf("Correct brackets!\n");
	}		
}