7/5

Author: Kang-bh

leetcode3/강병호/233_Number of Digit One.java

@@ -0,0 +1,26 @@
+class Solution {
+    public int countDigitOne(int n) {
+        int count = 0;
+        long factor = 1; 
+
+        while (factor <= n) {
+            long divider = factor * 10;
+            long higher = n / divider;
+            long current = (n / factor) % 10;
+            long lower = n % factor;
+            
+            if (current == 0) {
+                count += higher * factor;
+            } else if (current == 1) {
+                count += (higher * factor) + (lower + 1);
+            } else {
+                count += (higher + 1) * factor;
+            }
+            
+            if (n / 10 < factor) break; 
+            factor *= 10;
+        }
+        
+        return count;
+    }
+}