problems(cpp): add “744. Find Smallest Letter Greater Than Target”

Signed-off-by: Matej Focko <mfocko@redhat.com>

problems/cpp/find-smallest-letter-greater-than-target.cpp

@@ -0,0 +1,23 @@
+#include <algorithm>
+#include <cassert>
+#include <vector>
+
+class Solution {
+public:
+    char nextGreatestLetter(const std::vector<char>& letters, char target)
+    {
+        auto it = std::lower_bound(letters.begin(), letters.end(), target + 1);
+        return it == letters.end() ? letters.front() : *it;
+    }
+};
+
+int main()
+{
+    Solution s;
+
+    assert((s.nextGreatestLetter(std::vector { 'c', 'f', 'j' }, 'a') == 'c'));
+    assert((s.nextGreatestLetter(std::vector { 'c', 'f', 'j' }, 'c') == 'f'));
+    assert((s.nextGreatestLetter(std::vector { 'x', 'x', 'y', 'y' }, 'z') == 'x'));
+
+    return 0;
+}