java: add «1945. Sum of Digits of String After Convert»

Signed-off-by: Matej Focko <me@mfocko.xyz>

java/sum-of-digits-of-string-after-convert.java

@@ -0,0 +1,23 @@
+class Solution {
+  public int getLucky(String s, int k) {
+    // First iteration
+    int lucky = 0;
+    for (var c : s.toCharArray()) {
+      var number = c - 'a' + 1;
+      while (number > 0) {
+        lucky += number % 10;
+        number /= 10;
+      }
+    }
+
+    for (int i = 1; i < k; ++i) {
+      var nextLucky = 0;
+      for (; lucky > 0; lucky /= 10) {
+        nextLucky += lucky % 10;
+      }
+      lucky = nextLucky;
+    }
+
+    return lucky;
+  }
+}