Why am I not getting the right output?

Question

I'm trying to count the number of inversions in an array. I'm getting the result of 3 when it should be 4. Here's my code.

 int[] array1 = new int[5];
 array1[0] = 3;
 array1[1] = 7;
 array1[2] = 10;
 array1[3] = 6;
 array1[4] = 4;

 int count = 0;
for(int i =0;i<array1.length;i++){

    for(int j =i+1;j<array1.length;j++){

        if(array1[i]> array1[j] ){

        count++;
    }
}
}
System.out.println(count);

Anyone know why its doing this? thanks

ArrayIndexOutOfBoundException here. You are incrementing 'i' up to array1.length. It should be '<' not '<=' — Andrew Lobley, Nov 08 '15 at 22:24
why i++ j++ inside for loop. please check for loop increment logic. — bakki, Nov 08 '15 at 22:25
As mentioned in the previous comments, you need to remove those variable increments at the end of each for loop, and change the "<=" symbols to "<". — Walker Christie, Nov 08 '15 at 22:28
What is it exactly you are trying to accomplish with the loops? — Alexander, Nov 08 '15 at 22:35
sorry its actually 5 i'm after, 7>6, 7>4, 10>6, 10>4 and 6>4 — lc112, Nov 08 '15 at 22:36
that makes no sense. where is the value of array1[0] being compared? — Alexander, Nov 08 '15 at 22:42

score 0 · Answer 1 · answered Nov 08 '15 at 22:27

0

The i++ and j++ index incrementation should not be repeated in the body of your for loops as they already exist in the same line of the for loop conditions.

answered Nov 08 '15 at 22:27

Ling Zhong

1,744
14
24

Andrew Lobley · Accepted Answer · 2015-11-08T22:43:44.030

0

Remove j++ and i++. Also change the initial position of j to i+1, instead of 0.

int[] array1 = new int[5];
array1[0] = 3;
array1[1] = 7;
array1[2] = 10;
array1[3] = 6;
array1[4] = 4;

int count = 0;
for(int i =0;i<array1.length;i++){

    for(int j=i+1;j<array1.length;j++){

       if(array1[i]> array1[j] ){
          count++;
       }

    }
 }
 System.out.println(count);

edited Nov 08 '15 at 22:43

answered Nov 08 '15 at 22:39

Andrew Lobley

342
4
12

I had done what you suggested before hand and I was getting 6, but from changing j from 1 to i + 1 it worked :d thanks a lot – lc112 Nov 08 '15 at 22:42

Why am I not getting the right output?

2 Answers2