Comparing previous array elements for Insertion Sort algorithm

Question

I'm working with insertion sort algorithm. As you know we need to compare array elements with previous array elements. I try to do this with nested loops:

scanf("%d", &size); //gets array size

int array[size];
int temp = 0;

for (int i = 0; i < size; i++) {
    scanf("%d", &array[i]);
} // Takes the index of array.

/*
 Sorting part begins.
 */

for (int j = size - 1; j <= 0; j--) {
    int pseudoJ;

    pseudoJ = j;

    while (1) {
        if (array[pseudoJ] < array[pseudoJ - 1]) {
            temp = array[pseudoJ];
            array[pseudoJ] = array[pseudoJ - 1];
            array[pseudoJ - 1] = temp;
            pseudoJ--;
        } else
            break;
    }  
}

/*
 * Sorting Par Ends.
 */

Assume that input is: 3(Array Elements)>3>2>1, I expected the output of 1>2>3 but the output is still 3>2>1.

Take a very good look at the boundary condition of your second for loop. — NPE
– NPE, Commented Apr 5, 2019 at 7:55
Yes, when I change few lines of code it compares the previous array element but did not compare with all the previous ones.. — Levent Kaya
– Levent Kaya, Commented Apr 5, 2019 at 7:57

chqrlie · Accepted Answer · 2019-04-05 08:05:15Z

1

The posted code has multiple problems:

the outer loop exits immediately: the test should be j > 0 instead of j <= 0.
the inner loop should test pseudoJ to avoid accessing elements before the beginning of the array
it would be simpler to increment the index j in the outer loop and decrement i in the inner loop. The name pseudoJ is confusing.

answered Apr 5, 2019 at 8:05

chqrlie

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1 Comment

Levent Kaya Over a year ago

Thank you for contribution!

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