zoukankan      html  css  js  c++  java
  • 【Leetcode】38. Count and Say

    Question:

    The count-and-say sequence is the sequence of integers with the first five terms as following:
    
    1.     1
    2.     11
    3.     21
    4.     1211
    5.     111221
    
    1 is read off as "one 1" or 11.
    11 is read off as "two 1s" or 21.
    21 is read off as "one 2, then one 1" or 1211.
    
    Given an integer n, generate the nth term of the count-and-say sequence.
    
    Note: Each term of the sequence of integers will be represented as a string.
    
    Example 1:
    
    Input: 1
    Output: "1"
    
    Example 2:
    
    Input: 4
    Output: "1211"

    Leedcode提交代码:Runtime: 19 ms

    StringBuilder curr=new StringBuilder("1");
            StringBuilder ans;
            //if(n==1) return "1";
            int temp;
            char a;
            for(int i=1;i<n;i++){//循环n
                ans=curr;
                curr=new StringBuilder();
                temp=1;
                int length=ans.length();
                a=ans.charAt(0);
                for(int j=1;j<length;j++){//循环上一个ans
                    
                    if(ans.charAt(j)!=a){
                        curr.append(temp).append(a).toString();
                        temp=1;
                        a=ans.charAt(j);
                        //System.out.println(ans);
                    }else{
                        temp++;
                    }
                    
                }
                curr.append(temp).append(a);
            }
            System.out.println(curr);
            return curr.toString();

    完整可运行代码:

    package easy;
    
    public class L38 {
        public String countAndSay(int n) {
            StringBuilder curr=new StringBuilder("1");
            StringBuilder ans;
            //if(n==1) return "1";
            int temp;
            char a;
            for(int i=1;i<n;i++){//循环n
                ans=curr;
                curr=new StringBuilder();
                temp=1;
                int length=ans.length();
                a=ans.charAt(0);
                for(int j=1;j<length;j++){//循环上一个ans
                    
                    if(ans.charAt(j)!=a){
                        curr.append(temp).append(a).toString();
                        temp=1;
                        a=ans.charAt(j);
                        //System.out.println(ans);
                    }else{
                        temp++;
                    }
                    
                }
                curr.append(temp).append(a);
            }
            System.out.println(curr);
            return curr.toString();
        }
    
        public static void main(String[] args) {
            L38 l38 = new L38();
            l38.countAndSay(9);
        }
    }

    注:

    ①最开始使用一个String变量ans进行循环,导致每轮次ans之间混乱,加入curr变量,解决这个问题。

    ② String与StringBuilder之间的区别:

        String:字符串常量

        StringBuffer:字符串变量

    String s = "abcd";//创建名为s的String类型变量 abcd
    s = s+1;//创建新的对象s 赋值为abcd1
    System.out.print(s);// result : abcd1

        StringBuilder:线程非安全的

        StringBuffer:线程安全的

                  1.如果要操作少量的数据用 = String

                            2.单线程操作字符串缓冲区 下操作大量数据 = StringBuilder

                            3.多线程操作字符串缓冲区 下操作大量数据 = StringBuffer

    当stringBuilder全部变成String可运行代码:Runtime: 63 ms

    String curr=new String("1");
            String ans;
            //if(n==1) return "1";
            int temp;
            char a;
            for(int i=1;i<n;i++){//循环n
                ans=curr;
                curr=new String();
                temp=1;
                int length=ans.length();
                a=ans.charAt(0);
                for(int j=1;j<length;j++){//循环上一个ans
                    
                    if(ans.charAt(j)!=a){
                        curr+=temp;
                        curr+=a;
                        temp=1;
                        a=ans.charAt(j);
                        //System.out.println(ans);
                    }else{
                        temp++;
                    }
                    
                }
                curr+=temp;
                curr+=a;
            }
            System.out.println(curr);
            return curr;
  • 相关阅读:
    Ubuntu 16.04安装迅雷(兼容性不高)
    Ubuntu 16.04安装QQ(不一定成功)
    Ubuntu查看隐藏文件夹的方法
    Ubuntu下非常规方法安装绿色软件(压缩包)
    Ubuntu下常规方法安装软件
    Ubuntu 16.04下截图工具Shutter
    java中 awt Graphics2D
    Vue2.0总结———vue使用过程常见的一些问题
    MySQL 中隔离级别 RC 与 RR 的区别
    DBAplus社群线上分享----Sharding-Sphere之Proxy初探
  • 原文地址:https://www.cnblogs.com/yumiaomiao/p/7087375.html
Copyright © 2011-2022 走看看