238. Product of Array Except Self

Author: TonyKim9401

product-of-array-except-self/TonyKim9401.java

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+class Solution {
+    public int[] productExceptSelf(int[] nums) {
+        // time complexity: O(n)
+        // space complexity: O(n)
+        int[] left = new int[nums.length];
+        int[] right = new int[nums.length];
+
+        // nums =  [1,  2,  3, 4]
+
+        // left =  [1,  1,  2, 6]
+        // right = [24, 12, 4, 1]
+
+        // nums => [24, 12, 8, 6]
+        left[0] = 1;
+        for (int i = 1; i < nums.length; i++) {
+            left[i] = left[i-1] * nums[i-1];
+        }
+
+        right[right.length-1] = 1;
+        for (int i = nums.length - 2; i >= 0; i--) {
+            right[i] = right[i+1] * nums[i+1];
+        }
+
+        for (int i = 0; i < nums.length; i++) {
+            nums[i] = left[i] * right[i];
+        }
+        return nums;
+    }
+}