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Without using arraylists, arraycopy, or any other imported method, but simply just using for loops and an additional array, how does one remove the first occurrence of a certain element?

this is my code so far: 

public class remover {
public static void main(String[] args) {
     //initial array
    int[] oldArray = {1,2,3,4};

    //value to remove is 3


    //define the new array with smaller size
    int[] newArray = new int[oldArray.length];

    //cycle through array
    for(int i=0;i < oldArray.length;i++) 
    {
        if(oldArray[i] == 3) {
            for(int k=0; k<i; k++) {
                newArray[i] = oldArray[i];
            }
            for(int m=i; m<oldArray.length; m++) {
                newArray[m] = oldArray[m];
            }


        }

    }


for(int i=0; i<oldArray.length; i++) {
System.out.println(oldArray[i]);
}
}
}
Adam
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    What have you tried..?? – Gokul Nath KP Oct 02 '18 at 04:05
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    Welcome to SO! Are you trying to copy the old array to a new one without the target element or are you trying to modify the old array in-place? What if there are multiple matches for the element to remove? Remove them all or just the first? – ggorlen Oct 02 '18 at 04:06
  • Why do you have such odd, arbitrary requirements? – Phil Oct 02 '18 at 04:06
  • @Phil I think that question could be asked about most questions on SO. – Adam Oct 02 '18 at 04:07
  • @Adam too true, but why do you? – Phil Oct 02 '18 at 04:08
  • @ggorlen Exactly! Trying to copy the old array into a new one without the target element. Then I'll just assign the old array reference to the new one. Just the first occurrence. – Adam Oct 02 '18 at 04:40

1 Answers1

2

Loop through twice like this

    int[] oldArray = {1,2,3,3,4};

    int valToremove = 3;
    int numToRemove = 0;

    for (int x : oldArray) {
        if (x == valToremove)
            numToRemove++;
    }

    //define the new array with smaller size
    int[] newArray = new int[oldArray.length - numToRemove];

    //cycle through array
    int i = 0;
    for (int x : oldArray) {
        if (x != valToremove) {
            newArray[i] = x;
            i++;
        }
    }
Scary Wombat
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  • Hey, I'm only trying to do it for the first occurrence. Wouldn't this delete all occurrences from the array? – Adam Oct 02 '18 at 04:50
  • @Adam I was showing how to be flexible with your code. If you only have one element then this code would still work. If you want to change your requirements to only remove the **first** matching number then this can be easily achieved by adding a boolean variable `alreadyRemoved = false` which can be set to true when removed and the `if` becoming `if (x != valToremove || !alreadyRemoved) ` – Scary Wombat Oct 02 '18 at 04:54
  • I tried your code, and got arrayoutofbounds with numtoremove at 0. when I changed it to 1, it changed every element in the array to 0 – Adam Oct 02 '18 at 16:48
  • Yes, you should change `int valToremove = 3;` – Scary Wombat Oct 02 '18 at 23:54