2022-05-19 update: added "Calculate Digit Sum of a String"

Author: fartem

src/main/java/com/smlnskgmail/jaman/leetcodejava/easy/CalculateDigitSumOfAString.java

@@ -0,0 +1,36 @@
+package com.smlnskgmail.jaman.leetcodejava.easy;
+
+import java.util.ArrayList;
+import java.util.List;
+
+// https://leetcode.com/problems/calculate-digit-sum-of-a-string
+public class CalculateDigitSumOfAString {
+
+    private String s;
+    private final int k;
+
+    public CalculateDigitSumOfAString(String s, int k) {
+        this.s = s;
+        this.k = k;
+    }
+
+    public String solution() {
+        while (s.length() > k) {
+            List<String> groups = new ArrayList<>();
+            for (int i = 0; i < s.length(); i += k) {
+                groups.add(s.substring(i, i + Math.min(k, s.length() - i)));
+            }
+            StringBuilder newS = new StringBuilder();
+            for (String group : groups) {
+                int num = 0;
+                for (int i = 0; i < group.length(); i++) {
+                    num += group.charAt(i) - '0';
+                }
+                newS.append(num);
+            }
+            s = newS.toString();
+        }
+        return s;
+    }
+
+}

src/test/java/com/smlnskgmail/jaman/leetcodejava/easy/CalculateDigitSumOfAStringTest.java

@@ -0,0 +1,20 @@
+package com.smlnskgmail.jaman.leetcodejava.easy;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class CalculateDigitSumOfAStringTest {
+
+    @Test
+    public void defaultTest() {
+        assertEquals(
+                "135",
+                new CalculateDigitSumOfAString(
+                        "11111222223",
+                        3
+                ).solution()
+        );
+    }
+
+}