Refactor longestPalindrome function to use std namespace

leetcode/lc5/ExpandCentre.cpp

@@ -1,18 +1,18 @@
-
+
 class Solution {
 public:
         string longestPalindrome(string s) {
         if (s.length() <= 1) {
             return s;
-        }
+        }
 
         auto expand_from_center = [&](int left, int right) {
             while (left >= 0 && right < s.length() && s[left] == s[right]) {
                 left--;
                 right++;
-            }
+            }
             return s.substr(left + 1, right - left - 1);
-        };
+        };
 
         string max_str = s.substr(0, 1);
 
@@ -29,39 +29,7 @@ public:
         }
 
         return max_str;
-    }
-};
-
-class Solution {
-public:
-    std::string longestPalindrome(std::string s) {
-        if (s.length() <= 1) {
-            return s;
-        }
-
-        auto expand_from_center = [&](int left, int right) {
-            while (left >= 0 && right < s.length() && s[left] == s[right]) {
-                left--;
-                right++;
-            }
-            return s.substr(left + 1, right - left - 1);
-        };
-
-        std::string max_str = s.substr(0, 1);
-
-        for (int i = 0; i < s.length() - 1; i++) {
-            std::string odd = expand_from_center(i, i);
-            std::string even = expand_from_center(i, i + 1);
-
-            if (odd.length() > max_str.length()) {
-                max_str = odd;
-            }
-            if (even.length() > max_str.length()) {
-                max_str = even;
-            }
-        }
-
-        return max_str;
-    }
-};
-
+
+    }
+};
+