Update 1067-digit-count-in-range.js

Author: everthis

1067-digit-count-in-range.js

@@ -1,3 +1,50 @@
+/**
+ * @param {number} d
+ * @param {number} low
+ * @param {number} high
+ * @return {number}
+ */
+const digitsCount = function(d, low, high) {
+  return countDigit(high, d) - countDigit(low - 1, d)
+};
+function countDigit(limit, d) {
+  let res = 0
+  const str = `${limit}`
+  const len = str.length
+  const { pow } = Math
+  if(d === 0) {
+    for(let i = 1; i < len; i++) {
+      const pre = ~~(limit / pow(10, i))
+      const post = pow(10, i - 1)
+      res += (pre - 1) * post
+      const e = +str[len - i]
+      if(e > d) {
+        res += post
+      } else if(e === d) {
+        res += (limit % post) + 1
+      }
+    }    
+  } else {
+    for(let i = 1; i <= len; i++) {
+      const pre = ~~(limit / pow(10, i))
+      const post = pow(10, i - 1)
+      res += pre * post
+      const e = +str[len - i]
+      if(e > d) {
+        res += post
+      } else if(e === d) {
+        res += (limit % post) + 1
+      }
+    }  
+  }
+  
+  
+  return res
+}
+
+
+// another
+
 /**
  * @param {number} d
  * @param {number} low