zoukankan      html  css  js  c++  java
  • LeetCode 650. 2 Keys Keyboard

    Initially on a notepad only one character 'A' is present. You can perform two operations on this notepad for each step:

    Copy All: You can copy all the characters present on the notepad (partial copy is not allowed).

    Paste: You can paste the characters which are copied last time.

    Given a number n. You have to get exactly n 'A' on the notepad by performing the minimum number of steps permitted. Output the minimum number of steps to get n 'A'.

    Example 1:

    Input: 3
    Output: 3
    Explanation:
    Intitally, we have one character 'A'.
    In step 1, we use Copy All operation.
    In step 2, we use Paste operation to get 'AA'.
    In step 3, we use Paste operation to get 'AAA'.

    Note:

    The n will be in the range [1, 1000].

    分析

    如果n是质数的话,就要一个一个粘贴上去,次数就是n.
    如果不是质数的话,由先由一个A获得n的最大公因子m为模版,在copy all,在paste n/m-1 次。

    class Solution {
    public:
        int isprime(int n){
            int i;
            if(n==1) return 1;
            for(i=2;i<=sqrt(n);i++)
                if(n%i==0) return i;
            return -1;
        }
        int minSteps(int n) {
            int dp[11001]={0};
            if(isprime(n)==-1)
               return n;
            for(int i=2;i<=n;i++)
                if(isprime(i)==-1)
                   dp[i]=i;
                else
                   dp[i]=dp[i/isprime(i)]+isprime(i);
            return dp[n];
        }
    };
    

    一种更棒的写法

    class Solution {
    public:
        int minSteps(int n) {
            if (n == 1) return 0;
            for (int i = 2; i < n; i++)
                if (n % i == 0) return i + minSteps(n / i);
            return n;
        }
    };
    
  • 相关阅读:
    2011年10月小记
    修改模拟器hosts文件
    2011年9月小记
    解决IIS7.5站点不能登录SQLEXPRESS
    EF 4.3 CodeBased Migrations
    2012年5月 小记
    Android对SD卡进行读写
    Tomcat for Eclipse
    ARR2.5 配置反向代理
    作业2浅谈数组求和java实验
  • 原文地址:https://www.cnblogs.com/A-Little-Nut/p/8439110.html
Copyright © 2011-2022 走看看