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| 1 | +// https://leetcode.com/problems/product-of-array-except-self |
| 2 | +// T: O(N) |
| 3 | +// S: O(1) |
| 4 | + |
| 5 | +public class ProductOfArrayExceptItself { |
| 6 | + |
| 7 | + private record ProductDetails(int nonZeroProduct, int numberOfZeros) { } |
| 8 | + |
| 9 | + public int[] productExceptSelf(int[] nums) { |
| 10 | + final ProductDetails productDetails = getProductDetails(nums); |
| 11 | + if (productDetails.numberOfZeros > 1) return new int[nums.length]; |
| 12 | + if (productDetails.numberOfZeros == 1) return productSumOnlyWhenZero(nums, productDetails.nonZeroProduct); |
| 13 | + final int[] result = new int[nums.length]; |
| 14 | + for (int i = 0 ; i < result.length ; i++) { |
| 15 | + result[i] = productDetails.nonZeroProduct / nums[i]; |
| 16 | + } |
| 17 | + return result; |
| 18 | + } |
| 19 | + |
| 20 | + private int[] productSumOnlyWhenZero(int[] array, int product) { |
| 21 | + final int[] result = new int[array.length]; |
| 22 | + for (int i = 0 ; i < array.length ; i++) { |
| 23 | + if (array[i] == 0) result[i] = product; |
| 24 | + } |
| 25 | + return result; |
| 26 | + } |
| 27 | + |
| 28 | + private ProductDetails getProductDetails(int[] array) { |
| 29 | + int numberOfZeros = 0; |
| 30 | + int nonZeroProduct = 1; |
| 31 | + for (int element : array) { |
| 32 | + if (element == 0) numberOfZeros++; |
| 33 | + else nonZeroProduct *= element; |
| 34 | + } |
| 35 | + return new ProductDetails(nonZeroProduct, numberOfZeros); |
| 36 | + } |
| 37 | +} |
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