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Cisco 两轮面经 (全印阵容)

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yi1san3fendi 发表于 2016-7-2 14:46:53 | 显示全部楼层 |阅读模式

2016(1-3月) 码农类 硕士 全职@Cisco - 内推 - 技术电面 |Failfresh grad应届毕业生

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Cisco网上自己投过,也找人内推过,一天突然一个印度recruiter发邮件过来联系电面,也不知是哪个起了作用
两轮面试后再无消息,3个多月过去了,估计是印度人把我当作炮灰做political correctness了

第一轮:一个印度人用webex给我电话面试,开视频,出了道 Phonebook 的 OO design, 并且有一些客户要求如果Phonebook上某些人联系方式改变,会被通知;我意识到用obeserver pattern,写了java code,  通过,说会有下一轮面试

第二轮:印度recruiter联系我,说onsite面试报销太麻烦(现在想起来应该是只不过准备把我当炮灰),说继续用webex video面试,但是需要一个下午时间,面试官全印阵容, 4个印度人-google 1point3acres
1. 有一堆文档,给一个单词,返回包含这个单词的所有文档路径,并且返回这些文档跟这个单词对应的instances
        word ->  <docPath1, docPath2, ..., docPathn>

package cisco;
import java.io.*;
import java.util.*;. visit 1point3acres.com for more.

public class Solution1 {//assume the doc path is unique, and we can use it as ID
    HashMap<String, HashMap<String, Integer>> wordPathHm;//<word, <docID/path, number of instances>>
    public Solution1(){. 1point 3acres 璁哄潧
        wordPathHm = new HashMap<String, HashMap<String, Integer>>();
    }. 鍥磋鎴戜滑@1point 3 acres
   
    public void buildIndex(String path) throws IOException{
        Scanner doc = new Scanner(new FileReader(path));
        while(doc.hasNextLine()){
            String line = doc.nextLine();
            String[] words = line.split("\\s+");. from: 1point3acres.com/bbs
            for(String word : words){
                if(wordPathHm.containsKey(word)){//if the word already exists, update the hashmap. 1point3acres.com/bbs
                    HashMap<String, Integer> oldlist = wordPathHm.get(word);.鏈枃鍘熷垱鑷1point3acres璁哄潧
                    Integer currCnt = oldlist.get(path);. visit 1point3acres.com for more.
                    oldlist.put(path, currCnt+1);. Waral 鍗氬鏈夋洿澶氭枃绔,
                } else {//if the word does not exist, add a new entry
                    HashMap<String, Integer> newlist = new HashMap<String, Integer>();. 1point 3acres 璁哄潧
                    newlist.put(path, 1);. 鍥磋鎴戜滑@1point 3 acres
                    wordPathHm.put(word, newlist);
                }
            }
        }
        doc.close();
    }
   
    public List<String> getDocsPaths(String word){
        List<String> paths = new ArrayList<String>();. 鐣欏鐢宠璁哄潧-涓浜╀笁鍒嗗湴
        if(wordPathHm.containsKey(word)){
            HashMap<String, Integer> hmRecord = wordPathHm.get(word);
            for(String docPath : hmRecord.keySet()){
                paths.add(docPath);
            }
        }
        
        return paths;
    }
   
    public int getDocInstanceNum(String word, String docPath){
        if(wordPathHm.containsKey(word)){
            HashMap<String, Integer> hmRecord = wordPathHm.get(word);
            if(hmRecord.containsKey(docPath)){
                return hmRecord.get(docPath);
            } else {
                return -2; //the doc does not exist
            }. visit 1point3acres.com for more.
        } else {
            return -1; // the word does not exist
        }        
    }

}

然后又问如果用户很多该怎么办
DHT
hash(docID/path) -> which server should be queried for this doc
    the queried server should return the path of the documents, and how many instances in each document 鏉ユ簮涓浜.涓夊垎鍦拌鍧.
multiple hashmaps. From 1point 3acres bbs
each hashmap return the number of instances for this key word, and add the count  together



2. 问了操作系统调度问题,我刚好看了一点
Completely Fair Scheduler   Linux 2.6
we have different priority weights for different tasks
it is difficult for us to predict how much time

previous exectuion time
virtual running time(vrt) = already execution time/ priority weights

build red-black tree -> an approximately balanced binary search tree
if vrt is smaller , it means it should be assigned to the processor earlier
start from leftmost nodes 鏉ユ簮涓浜.涓夊垎鍦拌鍧.

               18. visit 1point3acres.com for more.
        12           26
    4        16     20    28.鐣欏璁哄潧-涓浜-涓夊垎鍦

又问top K words
package cisco;
import java.io.FileReader;
import java.util.*;

public class Solution2 {
    public List<String> getTopKWords(String path, int k) throws Exception{. From 1point 3acres bbs
        List<String> result = new ArrayList<String>();.鏈枃鍘熷垱鑷1point3acres璁哄潧
        if(k <= 0)
            return result;
        Scanner doc = new Scanner(new FileReader(path));
        HashMap<String, Integer> wordCnt = new HashMap<String, Integer>();
        while(doc.hasNextLine()){ // find the total number of occurrences for each word
            String line = doc.nextLine();
            String[] words = line.split("\\s+");
            for(String word : words){
                   if(wordCnt.containsKey(word)){
                       wordCnt.put(word, wordCnt.get(word)+1);. 涓浜-涓夊垎-鍦帮紝鐙鍙戝竷
                   } else {
                       wordCnt.put(word, 1);
                   }
                }
        }
        doc.close();. Waral 鍗氬鏈夋洿澶氭枃绔,

        Set<Map.Entry<String, Integer>> set = wordCnt.entrySet();
        List<Map.Entry<String, Integer>> list = new ArrayList<Map.Entry<String, Integer>>(set);. more info on 1point3acres.com
        Collections.sort(list, new Comparator<Map.Entry<String, Integer>>(){
            @Override
            public int compare(Map.Entry<String, Integer> o1, Map.Entry<String, Integer> o2){
                return o2.getValue()-o1.getValue(); // from the highest occurrences to the lowest occurrences
            }
        });-google 1point3acres
        
        int upperbound = Math.min(k, list.size());
        for(int i=0; i<upperbound; i++){// if k is larger than the number of words, then return all words 鏉ユ簮涓浜.涓夊垎鍦拌鍧.
            result.add(list.get(i).getKey());
        }
        .1point3acres缃
        return result;
    }

}


最后还剩8分钟,拷贝粘贴扔给我一道大题,关于字符串编码解码的,题目文字描述其中还有一堆乱码;他说这题你还能用java来做?我跟他确认题目意思都用了8分钟;最后说我可以面试完后做了发给他(好吧,他拿到了java版本的答案,真精明) 为了方便大家看,我剔除乱码,整理如下:
Where Did Those Numbers Come From?.鐣欏璁哄潧-涓浜-涓夊垎鍦
In both modes, the program maintains a linked list of words that have appeared in the input. In compression mode, the program reads the next word from the input file and searches for it in the list. If it is not found, the program writes the word to the output file and inserts it at the front of the list. If the word is found in the i-th position in the list, the program writes out i, removes the word from the list, then reinserts it at the front (this is the move-to-front feature). For example, let us consider the text:
LOVE,   LOVE   ME   DO!      YOU   KNOW   I   LOVE   YOU,   YOU,   YOU.-google 1point3acres
which after compression becomes     
LOVE,   1   ME   DO!      YOU   KNOW   I   6   4,   1,   1.. visit 1point3acres.com for more.
Notice that LOVE is replaced by both 1 and 6, and that 1 replaces both LOVE and YOU. This is due to word insertions in the list and the effect of move-to-front. After the second LOVE is processed, the word list is simply 鏉ユ簮涓浜.涓夊垎鍦拌鍧.
(LOVE)
hence the second instance of LOVE is replaced by the number 1. After the I is processed, the word list is
(I, KNOW, YOU, DO, ME, LOVE)
Next, the third instance of LOVE is processed, the word is found in the 6th position (thus it is
replaced by number 6), and the list becomes:
(LOVE, I, KNOW, YOU, DO, ME)
When the second YOU is processed, YOU is found in the 4th position, and the list becomes:. more info on 1point3acres.com
(YOU, LOVE, I, KNOW, DO, ME) 鏉ユ簮涓浜.涓夊垎鍦拌鍧.
Finally, when the last two instances of YOU are processed, the word is found in the first position.
In decompression mode, a word read from input is written out again and inserted at the front of the list. When the number i is read, the word in the i-th position is written out, then the word is deleted from the list and reinserted at the front. Decompression ends when the number 0 is read. The decompressed version should be identical to the original in every respect! (In Unix, you can use the utility diff to check this.)


package cisco;

import java.util.*;. 鐗涗汉浜戦泦,涓浜╀笁鍒嗗湴

//the requirement does not specify "LOVE" or "love" is the same word, so I assume words are all in uppercase. 鐗涗汉浜戦泦,涓浜╀笁鍒嗗湴
public class MoveToFrontCoding {
    public String compression(String str) {
        LinkedList<String> list = new LinkedList<>();
        StringBuilder ret = new StringBuilder();
        int last = 0;.鐣欏璁哄潧-涓浜-涓夊垎鍦
        for (int i = 0; i < str.length(); i++) {. 1point 3acres 璁哄潧
            if (Character.toUpperCase(str.charAt(i)) >= 'A' && Character.toUpperCase(str.charAt(i)) <= 'Z') {
                continue;
            } else {
                if (last != i) {
                    String s = str.substring(last, i); 鏉ユ簮涓浜.涓夊垎鍦拌鍧.
                    int idx = list.indexOf(s);
                    if (idx >= 0) {// if the word already exists, replace it with a number
                        list.remove(idx);
                        ret.append(idx + 1);
                    } else {// if the word does not exist, keep it
                        ret.append(s);
                    }
                    list.offerFirst(s);//insert the word at the beginning
                }
                last = i + 1;
                ret.append(str.charAt(i));//insert the word at the beginning
            }
        }
        if (last != str.length()) {
            String s = str.substring(last, str.length());. 1point 3acres 璁哄潧
            int idx = list.indexOf(s);. 涓浜-涓夊垎-鍦帮紝鐙鍙戝竷
            if (idx >= 0) {// if the word already exists, replace it with a number
                list.remove(idx);
                ret.append(idx + 1);
            } else {// if the word does not exist, keep it
                ret.append(s);
            }
            list.offerFirst(s);//insert the word at the beginning. 1point 3acres 璁哄潧
        }
        return ret.toString();
    }

    public String decompression(String str) {
        LinkedList<String> list = new LinkedList<>();
        StringBuilder ret = new StringBuilder();
        int last = 0;
        for (int i = 0; i < str.length(); i++) {
            if ((str.charAt(i) >= '0' && str.charAt(i) <= '9') || (Character.toUpperCase(str.charAt(i)) >= 'A' && Character.toUpperCase(str.charAt(i)) <= 'Z')) {
                continue;
            } else {
                if (last != i) {
                    String ss = str.substring(last, i);
                    if (ss.matches("\\d+")) {//  the word already exists, replace the index with the word. visit 1point3acres.com for more.
                        int idx = Integer.parseInt(ss) - 1;. 鍥磋鎴戜滑@1point 3 acres
                        ret.append(list.get(idx));
                        String s = list.remove(idx);
                        list.offerFirst(s);//insert the word at the beginning. From 1point 3acres bbs
                    } else {
                        ret.append(ss);
                        list.offerFirst(ss);//insert the word at the beginning
                    }
                }
                last = i + 1;
                ret.append(str.charAt(i));
            }
        }
        if (last != str.length()) {
            String ss = str.substring(last, str.length());. From 1point 3acres bbs
            if (ss.matches("\\d+")) {//  the word already exists, replace the index with the word
                int idx = Integer.parseInt(ss) - 1;. 鍥磋鎴戜滑@1point 3 acres
                ret.append(list.get(idx));
                String s = list.remove(idx);. 鐣欏鐢宠璁哄潧-涓浜╀笁鍒嗗湴
                list.offerFirst(s);//insert the word at the beginning. 鐗涗汉浜戦泦,涓浜╀笁鍒嗗湴
            } else {
                ret.append(ss);
                list.offerFirst(ss);//insert the word at the beginning
            }
        }
        return ret.toString();
    }.鏈枃鍘熷垱鑷1point3acres璁哄潧

    public static void main(String[] args) {
        MoveToFrontCoding s = new MoveToFrontCoding();
        String originalStr = "LOVE, LOVE ME DO!!  YOU KNOW I LOVE YOU, YOU, YOU.";
        System.out.println("original string: ");
        System.out.println(originalStr);
        System.out.println("Compressing...");. 1point 3acres 璁哄潧
        String s1 = s.compression(originalStr);. Waral 鍗氬鏈夋洿澶氭枃绔,
        System.out.println(s1);
        System.out.println("Decompressing...");
        String s2 = s.decompression(s1);
        System.out.println(s2);
    }
}

. visit 1point3acres.com for more.

Result:. 1point3acres.com/bbs


original string: .鐣欏璁哄潧-涓浜-涓夊垎鍦
LOVE, LOVE ME DO!!  YOU KNOW I LOVE YOU, YOU, YOU.
Compressing...
LOVE, 1 ME DO!!  YOU KNOW I 6 4, 1, 1.
Decompressing....1point3acres缃
LOVE, LOVE ME DO!!  YOU KNOW I LOVE YOU, YOU, YOU.

3  这个印度人完全问我的项目经历. 鐣欏鐢宠璁哄潧-涓浜╀笁鍒嗗湴

4. 这个印度人问完我的项目经历,让我用两种方法做string reverse,并且分析每一步的复杂度

A fox jumped over the fence

package cisco;

public class Solution3 {
       public String reverseStr1(String input){
            String s = input.trim();
            int len = s.length();
            if(len == 0)
                return input;//the input only contains space, return it. visit 1point3acres.com for more.
            String[] arrStr = input.split("\\s+");  // compute O(n)  memory read O(n)  write O(n)
            StringBuilder sb = new StringBuilder();. more info on 1point3acres.com
            for(int i=arrStr.length-1; i>=0; i--){  // compute O(n)  memory read O(n)  write O(n)
                sb.append(arrStr[i]+" ");        
            }
            String result = new String(sb); //compute O(n)  read O(n)  write O(n). 鐣欏鐢宠璁哄潧-涓浜╀笁鍒嗗湴
            result = result.trim();// remove the last empty space  compute O(n) read O(n)  write O(1)
            return result;
       }
      
        public String reverseStr2(String input) {
            String s = input.trim();
            int len = s.length();
            if(len == 0)
                return input;//the input only contains space, return it
            char[] cArr = s.toCharArray();
            for(int i=0; i<len/2; i++){// reverse the whole string  compute O(n)  memory read O(n)  write O(n)
                char tmp = cArr[i];
                cArr[i] = cArr[len-1-i];. visit 1point3acres.com for more.
                cArr[len-1-i] = tmp;
            }
            
            int m=0;
            for(int i=0; i<=len; i++){
                /* reverse each substring delimited by space
                 * compute O(n)  memory read O(n)  write O(n)*/
                if(i==len || cArr[i]==' '){
                    int len1 = i-m;
                    for(int j=0; j<len1/2; j++){
                        char tmp1 = cArr[m+j];
                        cArr[m+j] = cArr[len1+m-1-j];. 1point 3acres 璁哄潧
                        cArr[len1+m-1-j] = tmp1;
                    }
                    m = i+1;
                }
            }
            
            return String.valueOf(cArr);. 涓浜-涓夊垎-鍦帮紝鐙鍙戝竷
        }      
}


现在感觉我完全在给印度人提供面试题答案了;还是分享给大家比较好

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八和九生 发表于 2016-7-2 14:55:55 | 显示全部楼层
关注一亩三分地公众号:
Warald_一亩三分地
我勒个去,这是new grad吗?感觉好难啊。。。. 1point3acres.com/bbs
楼主好厉害= =
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八和九生 发表于 2016-7-2 15:02:04 | 显示全部楼层
关注一亩三分地微博:
Warald
八和九生 发表于 2016-7-2 14:55
我勒个去,这是new grad吗?感觉好难啊。。。
楼主好厉害= =

楼主的top k words写的好棒啊= = 学习了。。。
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lajiwushi 发表于 2016-7-6 07:04:21 | 显示全部楼层
谢谢楼主的分享!!!
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yingchal 发表于 2016-9-30 12:20:46 | 显示全部楼层
谢谢楼主分享,第一题题干真的好长啊
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