why it gives exception in insertion sort using java if i put d--; statement before the swiping

Question

public class JavaApplication28 {
   public static void main(String[] args) {
      int arr[]={5,4,3,2,1};
      int n=arr.length;
      int d=0;
      for(int i=1;i<n;i++){
          d=i;
          while(d>0 && arr[d-1]>arr[d]){
              d--; 
              int temp=arr[d-1];
              arr[d-1]=arr[d];
              arr[d]=temp;

          } 
      }
      for(int k=0;k<n;k++){
         System.out.println(arr[k]);
      } 
   } 
}

It gives exception:

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -1
    at javaapplication28.JavaApplication28.main(JavaApplication28.java:23)
C:\Users\ASUS™\AppData\Local\NetBeans\Cache\8.2\executor-snippets\run.xml:53: Java returned: 1
BUILD FAILED (total time: 0 seconds)

`d=1` `d-- -> 0` `arr[d-1]`... – John3136 Apr 30 '18 at 03:00 — John3136, Apr 30 '18 at 03:00

Hardik · Answer 1 · 2018-04-30T05:34:36.507

0

you can put d--; statement after swapping. If you perform before swapping. lookup tracing.

d=0

iteration 1:

i=1, d=1(value of i)

In while(1(value of d)>0 && arr[0(d-1)]>arr[1]) condition true.

d--;(d having 0 value)

temp = arr[0-1] (access -1 element in arr)

But array bound start with 0 to array.length - 1.

edited Apr 30 '18 at 05:34

answered Apr 30 '18 at 03:12

Hardik

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How does this answer the question? – 4castle Apr 30 '18 at 03:51
I have a correction in code based on tracing code. – Hardik Apr 30 '18 at 05:26

score 0 · Answer 2 · answered Apr 30 '18 at 05:37

Your code contains

while(d>0 && arr[d-1]>arr[d]){
              d--; 
              int temp=arr[d-1];

Let's imagine that the value of d is 1. You will enter the while{} loop. Then you will subtract 1 from d which means d is now 0.

Then you try to get the array member at position 0-1 = -1. -1 is not a valid index since arrays start at 0 (zero).

why it gives exception in insertion sort using java if i put d--; statement before the swiping

2 Answers2