Data commit

Task/Happy-numbers/Modula-2/happy-numbers.mod2

@@ -0,0 +1,44 @@
+MODULE HappyNumbers;
+FROM InOut IMPORT WriteCard, WriteLn;
+
+CONST Amount = 8;
+VAR seen, num: CARDINAL;
+
+PROCEDURE SumDigitSquares(n: CARDINAL): CARDINAL;
+VAR sum, digit: CARDINAL;
+BEGIN
+    sum := 0;
+    WHILE n>0 DO
+        digit := n MOD 10;
+        n := n DIV 10;
+        sum := sum + digit * digit;
+    END;
+    RETURN sum;
+END SumDigitSquares;
+
+PROCEDURE Happy(n: CARDINAL): BOOLEAN;
+VAR i: CARDINAL;
+    seen: ARRAY [0..255] OF BOOLEAN;
+BEGIN
+    FOR i := 0 TO 255 DO
+        seen[i] := FALSE;
+    END;
+    REPEAT
+        seen[n] := TRUE;
+        n := SumDigitSquares(n);
+    UNTIL seen[n];
+    RETURN seen[1];
+END Happy;
+
+BEGIN
+    seen := 0;
+    num := 0;
+    WHILE seen < Amount DO
+        IF Happy(num) THEN
+            INC(seen);
+            WriteCard(num,2);
+            WriteLn();
+        END;
+        INC(num);
+    END;
+END HappyNumbers.