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Problem with infinite loop in c program

  1. Aug 29, 2013 #1
    Hi, I have a program that is entering a infinite loop in the last if else of this loop. The program is printing 3 endless times. Here is the code that generates it:
    Code (Text):
     else {
        for (j=1;j<n;j++) {
          if (j<=(n/2)) {
            a[1][j] = j-1;
            printf ("%d", a[1][j]);
          }
          else if (j=(n/2)+1) {
            a[1][j] = a[1][j-1];
            printf ("%d", a[1][j]);
            //printf ("%d", j);
            //break;
          }
          else if  {
             
            a[1][j] = a[1][j-1]-1;
            printf ("%d", a[1][j]);
            break;  
          }
        }
    The three should be printed twice in a row, once by the if and the second time by the middle else if. Then the else should print decreasing values until the for loop end.
    So, I don't understand why this is happening . J value it is 5 when it leaves the middle else if, which it is the correct value. Then it should not enter the last "else" in this iteration, since j needs to be bigger than (n/2)+1, which I expect to be (9/2)+1, which should be rounded to 5, so j should enter the last else only in the next iteration when it's value should be 6 and keep entering it for two more iterations, until it reaches the value of 9, which should end the for loop.

    Here is the link for the full code in the case someone can compile it:
    http://codepad.org/66MYRyRQ

    Thanks for any input.
     
  2. jcsd
  3. Aug 29, 2013 #2

    DavidSnider

    User Avatar
    Gold Member

    What are you trying to do?

    This code is very very difficult to read.
     
  4. Aug 29, 2013 #3

    D H

    User Avatar
    Staff Emeritus
    Science Advisor

    The code you entered is not the same as your code at codepad.org. The code you entered at this site isn't valid code. However, the bug is still present. Here it is:

    else if (j=(n/2)+1) ...

    You used a single '=' sign rather than two. With two you are comparing but with one you are assigning. You are assigning a value to j, and hence the infinite loop.

    A good compiler will tell you about this common mistake if you let it do so. Enable all common warnings when compiling and then pay attention to those warnings.
     
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