[Kyojin-Hwang] WEEK 02 solutions

climbing-stairs/Kyojin-Hwang.js

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+/**
+ * @param {number} n
+ * @return {number}
+ */
+var climbStairs = function(n) {
+  if (n <= 2) return n;
+
+  let prev1 = 1; 
+  let prev2 = 2; 
+
+  for (let i = 3; i <= n; i++) {
+    const curr = prev1 + prev2; 
+    prev1 = prev2;
+    prev2 = curr;
+  }
+
+  return prev2;
+};

product-of-array-except-self/Kyojin-Hwang.js

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+/**
+ * @param {number[]} nums
+ * @return {number[]}
+ */
+var productExceptSelf = function (nums) {
+  const n = nums.length;
+  const answer = new Array(n).fill(1);
+
+  // 왼쪽 곱 계산
+  let prefix = 1;
+  for (let i = 0; i < n; i++) {
+    answer[i] = prefix;
+    prefix *= nums[i];
+  }
+
+  // 오른쪽 곱 계산
+  let suffix = 1;
+  for (let i = n - 1; i >= 0; i--) {
+    answer[i] *= suffix;
+    suffix *= nums[i];
+  }
+
+  return answer;
+};

valid-anagram/Kyojin-Hwang.js

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+/**
+ * @param {string} s
+ * @param {string} t
+ * @return {boolean}
+ */
+var isAnagram = function(s, t) {
+    if (s.length !== t.length) return false;
+
+    const count = {};
+
+    for (let char of s) {
+        count[char] = (count[char] || 0) + 1;
+    }
+
+    for (let char of t) {
+        if (!count[char]) return false; // 없거나 개수가 0
+        count[char]--;
+    }
+
+    return true;
+};