Product Of Array Except Self Solutions

Author: naringst

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

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+/**
+ * @param {number[]} nums
+ * @return {number[]}
+ */
+
+/**
+ * Runtime: 124ms, Memory: 65.06MB
+ * Time complexity: O(n^2)
+ * Space complexity: O(n)
+ * -> answer 배열에 O(n)
+ * -> splicedArr 배열에 O(n)
+ */
+
+var productExceptSelf = function (nums) {
+  const totalProduct = nums.reduce((total, current) => total * current, 1);
+  const answer = Array(nums.length).fill(0);
+
+  for (let i = 0; i < nums.length; i++) {
+    answer[i] = totalProduct / nums[i];
+    if (nums[i] === 0) {
+      const splicedArr = nums.filter(function (_, index) {
+        return index !== i;
+      });
+      answer[i] = splicedArr.reduce((total, current) => total * current, 1);
+    }
+  }
+
+  return answer;
+};
+
+/**
+ * @param {number[]} nums
+ * @return {number[]}
+ */
+
+/**
+ * 위의 풀이는 0일 때마다 순회를 해야 하기 때문에 해당 부분을 0의 개수를 세어 처리하도록 변경한 풀이
+
+ * Runtime: 109ms, Memory: 63.45MB
+ * Time complexity: O(n)
+ * Space complexity: O(n)
+
+ */
+var productExceptSelf = function (nums) {
+  let totalProduct = 1;
+  let zeroCount = 0;
+  const answer = Array(nums.length).fill(0);
+
+  for (let numIndex = 0; numIndex < nums.length; numIndex++) {
+    if (nums[numIndex] === 0) {
+      zeroCount += 1;
+    } else {
+      totalProduct *= nums[numIndex];
+    }
+  }
+
+  for (let i = 0; i < nums.length; i++) {
+    if (nums[i] === 0) {
+      if (zeroCount - 1 > 0) {
+        answer[i] = 0;
+      } else {
+        answer[i] = totalProduct;
+      }
+    } else {
+      if (zeroCount > 0) {
+        answer[i] = 0;
+      } else {
+        answer[i] = totalProduct / nums[i];
+      }
+    }
+  }
+
+  return answer;
+};