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javaarraysalgorithmshift

Java, Shifting Elements in an Array

I have an array of objects in Java, and I am trying to pull one element to the top and shift the rest down by one.

Assume I have an array of size 10, and I am trying to pull the fifth element. The fifth element goes into position 0 and all elements from 0 to 5 will be shifted down by one.

This algorithm does not properly shift the elements:

Object temp = pool[position];

for (int i = 0; i < position; i++) {                
    array[i+1] = array[i];
}
array[0] = temp;

How do I do it correctly?

Solution

  • Assuming your array is {10,20,30,40,50,60,70,80,90,100}

    What your loop does is:

    Iteration 1: array[1] = array[0]; {10,10,30,40,50,60,70,80,90,100}

    Iteration 2: array[2] = array[1]; {10,10,10,40,50,60,70,80,90,100}

    What you should be doing is

    Object temp = pool[position];

for (int i = (position - 1); i >= 0; i--) {                
    array[i+1] = array[i];
}

array[0] = temp;