Added Product of Array solution

Author: nhistory

product-of-array-except-self/nhistory.js

@@ -0,0 +1,40 @@
+/**
+ * @param {number[]} nums
+ * @return {number[]}
+ */
+var productExceptSelf = function (nums) {
+  const len = nums.length;
+  const lastIndex = len - 1;
+
+  // Declare prefix, postfix array
+  let prefix = new Array(len).fill(1);
+  let postfix = new Array(len).fill(1);
+
+  // Iterate loop to add prefix[i-1]*nums[i] values into prefix array
+  prefix[0] = nums[0];
+  for (let i = 1; i < nums.length; i++) {
+    prefix[i] = prefix[i - 1] * nums[i];
+  }
+
+  // Iterate loop to add postfix[i]*nums[i-1] values into postfix array
+  postfix[lastIndex] = nums[lastIndex];
+  for (let i = lastIndex; i >= 1; i--) {
+    postfix[i - 1] = postfix[i] * nums[i - 1];
+  }
+
+  // Make output array with prefix and postfix arrays
+  let output = new Array(len).fill(1);
+
+  // First index value is equal to postfix[1]
+  output[0] = postfix[1];
+  // Last index value is equal to prefix[lastIndex-1]
+  output[lastIndex] = prefix[lastIndex - 1];
+  for (let i = 1; i < len - 1; i++) {
+    output[i] = prefix[i - 1] * postfix[i + 1];
+  }
+
+  return output;
+};
+
+// TC: O(n)
+// SC: O(n)