Solution for Product of Array Except Self #239

잊지말자 개행문자

Author: dohyeon2

product-of-array-except-self/dohyeon2.java

@@ -0,0 +1,49 @@
+import java.util.Arrays;
+
+class Solution {
+    // TC : O(n)
+    // SC : O(n)
+    public int[] productExceptSelf(int[] nums) {
+        /**
+         * Approach:
+         * 1. Calculate the product of all non-zero elements
+         * 2. Count how many zeros exist in the array.
+         * 3. Handle three cases:
+         * - If there are more than one zero, all results are 0.
+         * - If there is exactly one zero,
+         * only the index with 0 gets the total product; others are 0.
+         * - If there is no zero, each result is totalProduct / nums[i].
+         */
+        int zeroCount = 0;
+
+        for (int n : nums) {
+            if (n == 0) {
+                zeroCount++;
+            }
+            if (zeroCount > 1) {
+                break;
+            }
+        }
+
+        if (zeroCount > 1) {
+            return new int[nums.length];
+        }
+
+        int production = Arrays.stream(nums).filter((n) -> {
+            return n != 0;
+        }).reduce(1, (a, b) -> a * b);
+
+        if (zeroCount == 1) {
+            return Arrays.stream(nums).map((n) -> {
+                if (n == 0) {
+                    return production;
+                }
+                return 0;
+            }).toArray();
+        }
+
+        return Arrays.stream(nums).map((n) -> {
+            return production / n;
+        }).toArray();
+    }
+}