Create sum-of-digits-of-string-after-convert.cpp

Author: kamyu104

C++/sum-of-digits-of-string-after-convert.cpp

@@ -0,0 +1,21 @@
+// Time:  O(n + logn + log(logn) + ...) = O(n)
+// Space: O(1)
+
+class Solution {
+public:
+    int getLucky(string s, int k) {
+        int total = accumulate(cbegin(s), cend(s), 0,
+                               [](const auto& total, const auto& x) {
+                                   const auto num = x - 'a' + 1;
+                                   return total + num / 10 + num % 10;
+                               });
+        while (--k && total > 9) {
+            int new_total = 0;
+            for (; total; total /= 10) {
+                new_total += total % 10;
+            }
+            total = new_total;
+        }
+        return total;
+    }
+};