add solusion

0142.h

@@ -0,0 +1,20 @@
+#include "common.h"
+
+using namespace std;
+
+namespace s0142 {
+    //  Definition for singly-linked list.
+    struct ListNode {
+        int val;
+        ListNode *next;
+        ListNode() : val(0), next(nullptr) {}
+        ListNode(int x) : val(x), next(nullptr) {}
+    };
+    class Solution {
+    public:
+        ListNode *detectCycle(ListNode *head) {
+
+
+        }
+    };
+}

0242.h

@@ -0,0 +1,24 @@
+#include "common.h"
+
+using namespace std;
+
+namespace s0242 {
+
+    class Solution {
+public:
+    bool isAnagram(string s, string t) {
+        int a[26];
+        if (s.size() != t.size()) return false;
+        for (int i=0; i<26; i++)
+            a[i] = 0;
+        for (int i=0; i<s.size(); i++){
+            a[s[i]-'a']++;
+            a[t[i]-'a']--;
+        }
+        for (int i=0; i<26; i++) {
+            if (a[i] != 0) return false;
+        }
+        return true;
+    }
+    };
+}

common.h

@@ -1,2 +1,3 @@
 #include <vector>
-#include <unordered_map>
+#include <unordered_map>
+#include <string>