Create find-longest-awesome-substring.cpp

Author: kamyu104

C++/find-longest-awesome-substring.cpp

@@ -0,0 +1,24 @@
+// Time:  O(10 * n)
+// Space: O(1024)
+
+class Solution {
+public:
+    int longestAwesome(string s) {
+        static const int ALPHABET_SIZE = 10;
+        int result = 0, mask = 0;
+        vector<int> lookup(1 << ALPHABET_SIZE, s.length());
+        lookup[0] = -1;
+        for (int i = 0; i < s.length(); ++i) {
+            mask ^= 1 << (s[i] - '0');
+            if (lookup[mask] == s.length()) {
+                lookup[mask] = i;
+            }
+            result = max(result, i - lookup[mask]);  // no middle
+            for (int d = 0; d < ALPHABET_SIZE; ++d) {
+                result = max(result, i - lookup[mask ^ (1 << d)]);  // as middle
+            }
+            lookup[mask] = min(lookup[mask], i);
+        }
+        return result;
+    }
+};