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ProductOfArrayExceptSelf.java
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ProductOfArrayExceptSelf.java
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package Leetcode;
import java.util.Arrays;
/**
* @author kalpak
*
* Given an array nums of n integers where n > 1, return an array output such that output[i] is equal to the product of all the elements of nums except nums[i].
*
* Example:
*
* Input: [1,2,3,4]
* Output: [24,12,8,6]
* Constraint: It's guaranteed that the product of the elements of any prefix or suffix of the array (including the whole array) fits in a 32 bit integer.
*
* Note: Please solve it without division and in O(n).
*
* Follow up:
* Could you solve it with constant space complexity? (The output array does not count as extra space for the purpose of space complexity analysis.)
*
*/
public class ProductOfArrayExceptSelf {
public static int[] productExceptSelf(int[] nums) {
/**
* { 1, a[0], a[0]*a[1], a[0]*a[1]*a[2], }
* { a[1]*a[2]*a[3], a[2]*a[3], a[3], 1, }
*/
int[] result = new int[nums.length];
result[0] = 1;
for(int i = 1; i < nums.length; i++) {
result[i] = result[i - 1] * nums[i - 1];
}
int right = 1;
for(int i = nums.length - 1; i >= 0; i--) {
result[i] = result[i] * right;
right = right * nums[i];
}
return result;
}
public static void main(String[] args) {
int[] nums = new int[]{1, 2, 3, 4, 5};
System.out.println(Arrays.toString(productExceptSelf(nums)));
}
}