product-of-array-except-self solution

Author: 이호찬

product-of-array-except-self/lhc0506.js

@@ -0,0 +1,54 @@
+
+// 풀이 1
+// /**
+//  * @param {number[]} nums
+//  * @return {number[]}
+//  */
+// var productExceptSelf = function(nums) {
+//     let hasZero = false;
+//     const allProductNums = nums.reduce((acc, cur) => {
+//         if (cur === 0) {
+//             if (!hasZero) {
+//                 hasZero = true;
+//                 return acc;
+//             }
+
+//             return 0;
+//         }
+//         return acc * cur;
+//     }, 1);
+
+//     return nums.map(num => {
+//         if (num === 0) {
+//             return allProductNums;
+//         }
+
+//         return hasZero ? 0 : allProductNums / num;
+//     });
+// };
+
+//풀이 2
+/**
+ * @param {number[]} nums
+ * @return {number[]}
+ */
+var productExceptSelf = function(nums) {
+    const result = Array(nums.length).fill(1);
+
+    let beforeProductNum = 1;
+    for (let i = 0; i < nums.length; i++) {
+        result[i] *= beforeProductNum;
+        beforeProductNum *= nums[i];
+    }
+
+    let afterProductNum = 1;
+    for (let i = nums.length - 1; i >= 0; i--) {
+        result[i] *= afterProductNum;
+        afterProductNum *= nums[i];
+    }
+
+    return result;
+};
+
+
+//두 풀이 모두 시간 복잡도 O(n), 공간 복잡도는 O(n)