[jaekwang97] WEEK 02 Solutions

climbing-stairs/jaekwang97.java

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+class Solution {
+    public int climbStairs(int n) {
+        int[] dp = new int[n + 1];
+        if (n <= 3) return n;
+        dp[1] = 1;
+        dp[2] = 2;
+        dp[3] = 3;
+
+        for (int i = 4; i <= n; i++) {
+            dp[i] = dp[i - 1] + dp[i - 2];
+        }
+
+        return dp[n];
+    }
+}

product-of-array-except-self/jaekwang97.java

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+import java.util.*;
+
+class Solution {
+    public int[] productExceptSelf(int[] nums) {
+        int n = nums.length;
+        int[] right = new int[n + 1];
+        int[] left = new int[n + 1];
+
+        right[0] = 1;
+        for (int i = 1; i <= n; i++) {
+            right[i] = right[i - 1] * nums[i - 1];
+        }
+
+        left[n] = 1;
+        for (int i = n - 1; i >= 0; i--) {
+            left[i] = left[i + 1] * nums[i];
+        }
+
+        int[] answer = new int[n];
+        for (int i = 0; i < n; i++) {
+            answer[i] = right[i] * left[i + 1];
+        }
+
+        return answer;
+    }
+}

valid-anagram/jaekwang97.java

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+import java.util.*;
+
+class Solution {
+    public boolean isAnagram(String s, String t) {
+        int[] count = new int[26];
+
+        for (char c : s.toCharArray()) {
+            count[c - 'a']++;
+        }
+
+        for (char c : t.toCharArray()) {
+            count[c - 'a']--;
+        }
+
+        for (int n : count) {
+            if (n != 0) return false;
+        }
+
+        return true;
+    }
+}