Array problem

Creamy Goodness

i have a 2d array of a fixed size, say 5 x 5 and i assign it random values. i want to be able to ask the user how many numbers they want to turn to 0 and then zero elements in the array. for example...

the array looks like this.

4, 5, 6, 7, 8,
2, 12, 345, 554, 32,
6, 3, 1, 7, 3,
122, 145, 312 ,211, 111,
999, 223, 221, 111, 124

i want to then ask the user to input a value between 0-25 and have it zero out the elements based on this number. so if the user inputs 4 the array will look like this.

4, 0, 0, 0, 0,
2, 12, 345, 554, 32,
6, 3, 1, 7, 3,
122, 145, 312 ,211, 111,
999, 223, 221, 111, 124

or if they enter in greater than 5 elements i.e. 8 elements, the array looks like this:

0, 0, 0, 0, 0,
2, 12, 0, 0, 0,
6, 3, 1, 7, 3,
122, 145, 312 ,211, 111,
999, 223, 221, 111, 124

below is what i've got so far, i know it's wrong and i'm probably overlooking something so simple and just can't see it. what the code below does is it zeros out everything.

#include <stdio.h>

int main(int argc, char** argv)
{
    int array[5][5] = {    4, 5, 6, 7, 8,
                    2, 12, 345, 554, 32,
                    6, 3, 1, 7, 3,
                122, 145, 312 ,211, 111,
                999, 223, 221, 111, 124
              };
    int i, j ;
    int user_input = 0;
    int loop_counter = 0;    

    printf("How many values do you want to zero out?\n");
    scanf("%d",&user_input);



    for(i = 0 ; i < 5 ; i++)
    {
        for(j = 5 ; j >= 0 ; j--)
        {
            array[i][j] = 0 ; 
            loop_counter++;
            printf("element [%d,%d] has the value of %d\n", i, j, array[i][j]);
        }
        
        if(loop_counter == user_input)
            break;

    }
}

anyone have any ideas?

Delirium

for(i = 0 ; i < 5 ; i++)
    {
        for(j = 5 ; j >= 0 ; j--)
        {
            array[i][j] = 0 ; 
            loop_counter++;
            printf("element [%d,%d] has the value of %d\n", i, j, array[i][j]);
        }
 
        if(loop_counter == user_input)
            break;
 
    }

I would think the if statement and break should be inside the inner for loop.

for(i = 0 ; i < 5 ; i++)
    {
        for(j = 5 ; j >= 0 ; j--)
        {
            array[i][j] = 0 ; 
            loop_counter++;
            printf("element [%d,%d] has the value of %d\n", i, j, array[i][j]);
 
            if(loop_counter == user_input)
              break;
 
        }
 
 
    }

hussey

Not quite ..
the logic above is correct the loop needs to break on the 2nd loop and 1st

teh break would only break out of the 2nd loop and 1st would continue

the reason is the loop would go like this

<do 5 iterations of inner loop>
check the break
<do another 5>

so if it was 4 the user typed in
if(loop_counter == user_input) = if (5 == 4)

also you have
for(j = 5 ; j >= 0 ; j--) array[j] = 0 ;

would this not look for array[0][5] first?? throw a Null pointer as it should be [0][4] first

boolean breakFlag = true;

        for(i = 0 ; i < 5 && breakFlag; i++)
        {
            for(j = 4 ; j >= 0 && breakFlag; j--)
            {
                array[i][j] = 0 ; 
                loop_counter++;
                System.err.println("element ["+i+","+j+"] has the value of " + array[i][j]);
                
                if(loop_counter == user_input)
                    breakFlag = false;
            }     
        }

works

LARDO

hussey wrote: »

Not quite ..
the logic above is correct the loop needs to break on the 2nd loop and 1st

teh break would only break out of the 2nd loop and 1st would continue

the reason is the loop would go like this

<do 5 iterations of inner loop>
check the break
<do another 5>

so if it was 4 the user typed in
if(loop_counter == user_input) = if (5 == 4)

also you have
for(j = 5 ; j >= 0 ; j--) array[j] = 0 ;

would this not look for array[0][5] first?? throw a Null pointer as it should be [0][4] first

boolean breakFlag = true;

        for(i = 0 ; i < 5 && breakFlag; i++)
        {
            for(j = 4 ; j >= 0 && breakFlag; j--)
            {
                array[i][j] = 0 ; 
                loop_counter++;
                System.err.println("element ["+i+","+j+"] has the value of " + array[i][j]);
                
                if(loop_counter == user_input)
                    breakFlag = false;
            }     
        }

works

some compilers have different ideas of operator precedence and may evaluate "j >= 0 && breakFlag" in an unanticipated way ie not left to right,
"(j >= 0) && breakFlag is safer.

Creamy Goodness

cheers guys that works.

i'm now trying to get this part working.

i ask the user how many elements they want to display first of all. and then ask them how many they want to zero out.

so it looks like this.

#include <stdio.h>

int main(int argc, char** argv)
{
    int array[5][5] = {    4, 5, 6, 7, 8,
                    2, 12, 345, 554, 32,
                    6, 3, 1, 7, 3,
                122, 145, 312 ,211, 111,
                999, 223, 221, 111, 124
              };
    int i, j ;
    int user_input = 0;
    int loop_counter = 0;    
   
    printf("how many values of the array do you want to display?\n");
    scanf("%d", &user_input);

    //print the array for how many elements they want to display.
    for(i = 0 ; i < 5 ; i++)
    {
          for(j = 0 ; j < user_input ; j++)
          {
                 printf("element [%d,%d] has the value of %d\n", i, j, array[i][j]);
           }
    }       



    printf("How many values do you want to zero out?\n");
    scanf("%d",&user_input);

   int flag = 1
    for(i = 0 ; (i < 5) && flag == 1  ; i++)
    {
        for(j = 4 ; (j >= 0) && flag == 1 ; j--)
        {
            array[i][j] = 0 ; 
            loop_counter++;
            printf("element [%d,%d] has the value of %d\n", i, j, array[i][j]);
        }
        
        if(loop_counter == user_input)
            break;

    }
}

so a sample run of the program would run like this:

How many elements do you wish to display: 7
4, 5, 6, 7, 8,
2, 12

how many elements do you wish to zero out: 6
0, 0, 0, 0, 0,
2, 0

Ri_Nollaig

    int size = 5;  

    ...

    printf("How many values do you want to zero out?\n");
    scanf("%d",&user_input);
   
    for(i = 0 ; i < size; i++)
    {
        for(j = size - 1; j >= 0; j--)
        {
 
            if(loop_counter != user_input) {
               array[i][j] = 0 ; 
               loop_counter++;
            }
            printf("%d ",  array[i][((size - j) - 1)]);
        }
        printf("\n");
    }
}

im at work so cant test, but I think that should work for you.