routine

25/12/comp/28q3.cpp

@@ -0,0 +1,17 @@
+class Solution {
+public:
+    int minAllOneMultiple(int k) {
+        if (k%2==0 || k%5==0) {
+            return -1;
+        }
+        int remainder = 1;
+        for (int i = 1 ;i<=k;i++) {
+            if (remainder % k == 0) {
+                return i;
+            }
+            // (a * 10 + 1) % k = ((a % k) * 10 + 1) % k
+            remainder = (remainder * 10 + 1) % k;
+        }
+        return -1;
+    }
+};