Update find-the-closest-palindrome.cpp

Author: kamyu104

Diff for: C++/find-the-closest-palindrome.cpp

@@ -5,20 +5,18 @@ class Solution {
 public:
     string nearestPalindromic(string n) {
         const auto l = n.size();
-        vector<long long> candidates;
-        candidates.emplace_back(static_cast<long long>(pow(10, l)) + 1);
-        candidates.emplace_back(static_cast<long long>(pow(10, l - 1)) - 1);
+        unordered_set<long long> candidates;
+        candidates.emplace(static_cast<long long>(pow(10, l)) + 1);
+        candidates.emplace(static_cast<long long>(pow(10, l - 1)) - 1);
         auto prefix = stol(n.substr(0, (l + 1) / 2));
         for (long long i = -1; i <= 1; ++i) {
             auto p = to_string(prefix + i);
             auto pp = p + string(p.rbegin() + (l % 2), p.rend());
-            candidates.emplace_back(stol(pp));
+            candidates.emplace(stol(pp));
         }
         long long num = stol(n), closest_val = numeric_limits<long long>::max();
+        candidates.erase(num);
         for (const auto& val : candidates) {
-            if (val == num) {
-                continue;
-            }
             if (abs(val - num) < abs(closest_val - num)) {
                 closest_val = val;
             } else if (abs(val - num) == abs(closest_val - num)) {