Product of Array Except Self solution

Author: HoonDongKang

product-of-array-except-self/HoonDongKang.ts

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+/**
+ * [Problem]: [238] Product of Array Except Self
+ * (https://leetcode.com/problems/product-of-array-except-self/description/)
+ */
+
+function productExceptSelf(nums: number[]): number[] {
+  // 시간 복잡도 O(n^2)
+  // 공간 복잡도 O(n)
+  // 시간 초과로 실패
+  function doubleLoopFunc(nums: number[]): number[] {
+    return nums.map((_, i) => nums.reduce((acc, cur, j) => (i === j ? acc : acc * cur), 1));
+  }
+
+  // 시간 복잡도 O(n)
+  // 공간 복잡도 O(n)
+  function separateFunc(nums: number[]): number[] {
+    const length = nums.length;
+    const result: number[] = new Array(length).fill(1);
+    let leftProduct = 1;
+    let rightProduct = 1;
+
+    for (let i = 0; i < length; i++) {
+      result[i] = leftProduct;
+      leftProduct *= nums[i];
+    }
+
+    for (let i = length - 1; i >= 0; i--) {
+      result[i] *= rightProduct;
+      rightProduct *= nums[i];
+    }
+
+    return result;
+  }
+
+  return separateFunc(nums);
+}