字节测开面经题汇总_字节 测开 算法题

1.判断是不是ipv6字符

import java.util.Scanner;

public class Zijie {
    public static void main(String[] args){
            Scanner sc=new Scanner(System.in);
            String str=sc.next();
            System.out.println(Isipv4(str));
       }
       public static boolean Isipv4(String ipv4){
           if(ipv4==null || ipv4.length()==0){       return false;//字符串为空或者空串
               }      String[] parts=ipv4.split("\\.");//因为java doc里已经说明, split的参数是reg, 即正则表达式, 如果用"|"分割, 则需使用"\\|"
           if(parts.length!=4){          return false;//分割开的数组根本就不是4个数字
               }      for(int i=0;i<parts.length;i++){
               try{
                   int n=Integer.parseInt(parts[i]);
                   if(n<0 || n>255){
                       return false;//数字不在正确范围内
                       }
               }catch (NumberFormatException e) {           return false;//转换数字不正确
               }      }     return true;

       }
}

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字符串中第一个不重复的字符

import java.util.*;

public class Zijie {
    public static void main(String[] args){
            Scanner input=new Scanner(System.in);
            String str=input.next();
            int index=firstNo(str);
            if(index==-1){
                System.out.println("没有");
                return;
            }
            System.out.println(str.charAt(index));
       }
       public static int firstNo(String str){
           Map<Character,Integer> map=new HashMap<Character, Integer>();
           for(int i=0;i<str.length();i++){
               char c=str.charAt(i);
               if(map.containsKey(c)){
                   map.put(c,map.get(c)+1);
               }else{
                   map.put(c,1);
               }
           }
           for(int i=0;i<str.length();i++){
               char c=str.charAt(i);
               if(map.get(c)==1){
                   return i;
               }
           }
           return -1;
       }
}

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手写top-K

import java.util.*;

public class Zijie {
    public static void main(String[] args) {
        //int a[] = {2, 20, 3, 7, 9, 1, 17, 18, 0, 4};
        //int k = 6;
        Scanner in=new Scanner(System.in);
        int num=in.nextInt();
        Scanner input=new Scanner(System.in);
        int i=0;
        int[] array=new int[num];
        while(i<num &&input.hasNextInt()){
            array[i]=input.nextInt();
            i++;
        }
        Scanner sc=new Scanner(System.in);
        int k=sc.nextInt();
        new TopK().getTopKMinBySort(array, 0, array.length - 1, k);
        for (int j = 0; j< k; j++) {
            System.out.print(array[j] + " ");
        }
    }
    //利用快速排序法
    public static class TopK {
        int partion(int a[], int first, int end) {
            int i = first;
            int main = a[end];
            for (int j = first; j < end; j++) {
                if (a[j] < main) {
                    int temp = a[j];
                    a[j] = a[i];
                    a[i] = temp;
                    i++;
                }
            }
            a[end] = a[i];
            a[i] = main;
            return i;
        }

        void getTopKMinBySort(int a[], int first, int end, int k) {
            if (first < end) {
                int partionIndex = partion(a, first, end);
                if (partionIndex == k - 1) return;
                else if (partionIndex > k - 1) getTopKMinBySort(a, first, partionIndex - 1, k);
                else getTopKMinBySort(a, partionIndex + 1, end, k);
            }
        }
    }
}

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最大连续子序列和

import java.util.*;

public class Zijie {
    int max;
    public static void main(String[] args) {
    Scanner sc=new Scanner(System.in);
    int num=sc.nextInt();
    sc.nextLine();
    Scanner sc2=new Scanner(System.in);
    int i=0;
    int[] array=new int[num];
    while(i<num &&sc2.hasNextInt()){
        array[i]=sc2.nextInt();
        i++;
    }
    System.out.println(maxSubArray(array));
    }
    public static int maxSubArray(int[] nums){
        if(nums==null ||nums.length<1){
            return 0;
        }
        int[] dp=new int[nums.length];
        dp[0]=nums[0];
        int max=nums[0];
        for(int i=1;i<nums.length;i++){
            dp[i]=Math.max(nums[i],dp[i-1]+nums[i]);
            if(dp[i]>max){
                max=dp[i];
            }
        }
        return max;
    }
}

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最长不连续子串

import java.util.*;

public class Zijie {

    public static void main(String[] args) {
    Scanner sc=new Scanner(System.in);
    String str=sc.next();

    System.out.println(lengthOfLongestSubstring(str));
    }
    public static int lengthOfLongestSubstring(String s) {
        int i = 0;
        int j = 0;
        int res = 0;

        Map<Character, Integer> map = new HashMap<Character, Integer>();

        while (j < s.length()) {
            char charJ = s.charAt(j);
            Integer cntJ = map.get(charJ);

            if (cntJ  == null || cntJ == 0) {
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