Create sequential-digits.cpp

Author: kamyu104

C++/sequential-digits.cpp

@@ -0,0 +1,23 @@
+// Time:  O((8 + 1) * 8 / 2) = O(1)
+// Space: O(8) = O(1)
+
+class Solution {
+public:
+    vector<int> sequentialDigits(int low, int high) {
+        vector<int> result;
+        queue<int> q{{1, 2, 3, 4, 5, 6, 7, 8}};
+        while (!q.empty()) {
+            const auto num = q.front(); q.pop();
+            if (num > high) {
+                continue;
+            }
+            if (low <= num) {
+                result.emplace_back(num);
+            }
+            if (num % 10 + 1 < 10) {
+                q.emplace(num * 10 + num % 10 + 1);
+            }
+        }
+        return result;
+    }
+};