[toychip] WEEK 02 solutions (#1240)

* contains-duplicate solution

* two-sum solution

* lint 오류 해결

* valid anagram solution

* climbin-stars solution

---------

Co-authored-by: junhyung <jhlim@suprema.co.kr>

Author: toychip

climbing-stairs/toychip.java

@@ -0,0 +1,23 @@
+class Solution {
+    public int climbStairs(int n) {
+        int[] memo = new int[n + 1];
+        return recur(n, memo);
+    }
+
+    int recur(int n, int[] memo) {
+        if (n < 0) {
+            return 0;
+        }
+
+        if (n == 0) {
+            return 1;
+        }
+
+        if (memo[n] > 0) {
+            return memo[n];
+        }
+
+        memo[n] = recur(n - 1, memo) + recur(n - 2, memo);
+        return memo[n];
+    }
+}

valid-anagram/toychip.java

@@ -0,0 +1,20 @@
+class Solution {
+    public boolean isAnagram(String s, String t) {
+        if (s.length() != t.length()) {
+            return false;
+        }
+
+        char[] sArray = s.toCharArray();
+        Arrays.sort(sArray);
+
+        char[] tArray = t.toCharArray();
+        Arrays.sort(tArray);
+
+        for (int i = 0; i < sArray.length; i++) {
+            if (sArray[i] != tArray[i]) {
+                return false;
+            }
+        }
+        return true;
+    }
+}