Update 233-number-of-digit-one.js

Author: everthis

233-number-of-digit-one.js

@@ -1,3 +1,31 @@
+/**
+ * @param {number} n
+ * @return {number}
+ */
+const countDigitOne = function(n) {
+  let res = 0
+  const str = `${n}`
+  const len = str.length, { pow } = Math
+  
+  for(let i = 1; i <= len; i++) {
+    const pre = ~~(n / pow(10, i))
+    const remain = n % (pow(10, i - 1))
+    const post = pow(10, i - 1)
+    res += pre * post
+    const e = +(str[len - i])
+    if(e > 1) {
+      res += pow(10, i - 1)
+    } else if(e === 1) {
+      res += remain + 1
+    }
+  }
+  
+  return res
+};
+
+
+// another
+
 /**
  * @param {number} n
  * @return {number}