ObjecÂtive: Given an array which contains even and odd integers. Write an algorithm to separate even and odd numbers.
Example
int [] arrA = {1,2,3,4,6,8,7,12};
Output: [12, 2, 8, 4, 6, 3, 7, 1]
Approach: Swapping Indexes
- Use two indexes, left and right.
- Put left index at the start of array and right at the end of the array.
- Increment left till odd number is not found.
- Decrement right till even number is not found.
- Swap left and right elements
- Do it till left<right
Time Complexity: O(n)
Code:
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| import java.util.Arrays; | |
| public class OddAndEven { | |
| public static int[] arrange(int [] arrA){ | |
| int left =0; | |
| int right = arrA.length–1; | |
| while(left<right){ | |
| if(arrA[left]%2==0) | |
| left++; | |
| else if(arrA[right]%2==1) | |
| right—; | |
| else{ | |
| //swap left and right elements | |
| int temp = arrA[left]; | |
| arrA[left] = arrA[right]; | |
| arrA[right] = temp; | |
| left++; | |
| right—; | |
| } | |
| } | |
| return arrA; | |
| } | |
| public static void main(String[] args) { | |
| int [] arrA = {1,2,3,4,6,8,7,12}; | |
| System.out.println("Rearranging arrays using left and right indexes"); | |
| arrA = arrange(arrA); | |
| System.out.println(Arrays.toString(arrA)); | |
| } | |
| } |
Output:
Rearranging arrays using left and right indexes [12, 2, 8, 4, 6, 3, 7, 1]