leetcode 357. Count Numbers with Unique Digits
来源:互联网 发布:mysql区分大小写查询 编辑:程序博客网 时间:2024/05/22 12:26
Given a non-negative integer n, count all numbers with unique digits, x, where 0 ≤ x < 10n.Example:Given n = 2, return 91. (The answer should be the total numbers in the range of 0 ≤ x < 100, excluding [11,22,33,44,55,66,77,88,99])
很好的解释
Following the hint. Let f(n) = count of number with unique digits of length n.f(1) = 10. (0, 1, 2, 3, ...., 9)f(2) = 9 * 9. Because for each number i from 1, ..., 9, we can pick j to form a 2-digit number ij and there are 9 numbers that are different from i for j to choose from.f(3) = f(2) * 8 = 9 * 9 * 8. Because for each number with unique digits of length 2, say ij, we can pick k to form a 3 digit number ijk and there are 8 numbers that are different from i and j for k to choose from.Similarly f(4) = f(3) * 7 = 9 * 9 * 8 * 7.......f(10) = 9 * 9 * 8 * 7 * 6 * ... * 1f(11) = 0 = f(12) = f(13)....any number with length > 10 couldn't be unique digits number.The problem is asking for numbers from 0 to 10^n. Hence return f(1) + f(2) + .. + f(n)
代码也很简单
public class Solution { public int countNumbersWithUniqueDigits(int n) { if(n==0) return 1; int res = 10; int cur = 9; int t = 10; while(n-->1 && t-- >=0){ cur *=t; res += cur; } return res; }}
阅读全文
0 0
- 【LeetCode】357. Count Numbers with Unique Digits
- LeetCode 357. Count Numbers with Unique Digits
- [leetcode] 357. Count Numbers with Unique Digits
- 【LeetCode】357. Count Numbers with Unique Digits
- leetcode 357. Count Numbers with Unique Digits
- leetcode 357. Count Numbers with Unique Digits
- leetcode.357. Count Numbers with Unique Digits
- LeetCode:357. Count Numbers with Unique Digits
- 【leetcode】357. Count Numbers with Unique Digits
- [leetcode] 357. Count Numbers with Unique Digits
- 357.[LeetCode]Count Numbers with Unique Digits
- [LeetCode]357. Count Numbers with Unique Digits
- LeetCode 357. Count Numbers with Unique Digits
- leetcode-357. Count Numbers with Unique Digits
- LeetCode 357. Count Numbers with Unique Digits
- [leetcode] 357. Count Numbers with Unique Digits
- Leetcode 357. Count Numbers with Unique Digits
- LeetCode 357. Count Numbers with Unique Digits
- TCP简单的通信
- angular2封装组件(一)——引用js包
- javascript中json、回调函数、匿名函数的一些测试
- 面向对象的六大原则解析
- cout.precision()的使用
- leetcode 357. Count Numbers with Unique Digits
- Fzu 2200 cleaning【环状Dp-----暴力枚举拆环】
- 最小二乘法
- 响铃:内容越发重要的时代,开放共享要成为智能电视的新玩法?
- echarts bar内tooltip的formatter回调参数params.seriesId中的’\0’问题以及stack的获取
- hdu1159 最长公共子序列 LCS
- 类型“Microsoft.VisualStudio.Tools.Office.Ribbon.View.GenericRibbonView”没有名为“Factory”的属性。
- svn 文件状态标记的含义
- 一个Native Service的完整示例