Goldman Sachs Interview Question for Senior Software Development Engineers


Country: United States




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9
of 9 vote

This can be done without any additional space in 2 pass
1) reverse the string in place
2) reverse each word of the reversed string.

- Varun April 11, 2013 | Flag Reply
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-1
of 1 vote

actually it is easier to implement if you switch the two steps

- athans June 20, 2013 | Flag
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1
of 1 vote

Time: O(n)
Space: O(n)

private static String getReversedSequence(String input) {
		StringBuffer output = new StringBuffer();
		
		int end_index = input.length();
		for (int i = end_index - 1; i >= 0; i--) {
			char space = input.charAt(i);
			if (space == ' ') {
				output.append(input.substring(i + 1, end_index));
				end_index = i;
				output.append(' ');
			}
		}
		output.append(input.substring(0, end_index));
		return output.toString();
	}

- Anonymous April 11, 2013 | Flag Reply
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1
of 1 vote

It is possible to do it in linear time and using constant space.

If you don't want to create a new string and just need to modify the one you have you can reverse characters in the string, and then reverse characters in each word.

If it is OK to create a new string you just need to go from the end of the original string and keep index of the end of the current word. And as soon as you reach any separate character simply copy each character from input string to output string from current index to word's end index and update word's end index.

- J. April 11, 2013 | Flag Reply
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1
of 3 vote

Push all the words in a stack and then pop the all out.

- alex April 11, 2013 | Flag Reply
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0
of 0 votes

Simple but not optimized. Can be done in place without O(n) memory.

- Karthik April 12, 2013 | Flag
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0
of 0 votes

if we follow your stack approach then for the input "Today is Wednesday" we get output as "yadsendeW si yadoT" but instead we need output as "Wednesday is Today"

- Gaurav June 10, 2013 | Flag
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0
of 0 votes

he is saying to push words in stack not individual characters ,....
he's right .

- coderpec August 13, 2013 | Flag
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1
of 1 vote

private void reverseString(String strValue) {
		
		List<String> lstWords = Arrays.asList(strValue.split(" "));
		Collections.reverse(lstWords);
		System.out.println(lstWords.toString().replaceAll(",", "").
				replace("[", "").replace("]", ""));
	}

- rizwan.amd April 11, 2013 | Flag Reply
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0
of 0 votes

Simple and nice

- Naruto August 24, 2013 | Flag
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0
of 0 vote

Guessing it in java:

String str = input; 
String str2 = "";
int lastIndexOfSpace = lastIndexOf(" ");
while (lastIndexOfSpace > 0){
	if (lastIndexOfSpace < length(str) - 1)
		str2 += str.substring(lastIndexOfSpace + 1) + " ";
	str = str.substring(0, lastIndexOfSpace);
}

- Anonymous April 11, 2013 | Flag Reply
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0
of 0 vote

def reverse(str):
s=str.split(" ")
s.reverse()
for i in s:
print(i end = " ")

- Anonymous April 11, 2013 | Flag Reply
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0
of 0 vote

x='Today is Wednesday'.split()
x.reverse()
' '.join(x)
print x

- Shaan April 11, 2013 | Flag Reply
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0
of 0 vote

This can be done in linear time.First reverse the sentence and then reverse the individual words.

Code:

public class ReverseSentence {
	public static void main(String[] args) {
		String a = "Today is Wednesday";
		a = a.trim();
		char[] cArr = a.toCharArray();
		ReverseSentence r = new ReverseSentence();
		r.reverse(cArr, 0, cArr.length-1);
		int s = 0;
		for (int i = 0; i < cArr.length; i++) {
			if (cArr[i] == ' ') {
				r.reverse(cArr, s, i - 1);
				s = i + 1;
			}
		}
		//call for the last word in the sentence
		r.reverse(cArr, s, cArr.length-1);
		System.out.println(cArr);
	}

	public void reverse(char c[], int i, int j) {
		char t;
		while (i < j) {
			t = c[i];
			c[i] = c[j];
			c[j] = t;
			i++;j--;
		}
	}
}

- Dhass April 11, 2013 | Flag Reply
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0
of 0 vote

import java.util.Scanner;
class demo
{
public static void main(String g[])
{
Scanner s = new Scanner(System.in);
System.out.println("Enter the String");
String s1 = s.nextLine();
String s2 ="";
		
		int end_index = s1.length();
		for (int i = end_index - 1; i >= 0; i--) {
			char space = s1.charAt(i);
			if (space == ' ') {
				s2 = s2 + s1.substring(i + 1, end_index);
				end_index = i;
				s2 = s2 + " ";
			}
		}
		s2 = s2 + s1.substring(0, end_index);;
		System.out.println(s2);
}
}

- shekhawat.amit1019 April 12, 2013 | Flag Reply
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0
of 0 vote

public void reverseSentence(String insentence) {
	char[] sentence = insentence.toCharArray();
	int[] blankposlist = new int[100];

	displayArray(sentence);
	int k = 0;
	blankposlist[k++] = -1;

	// storing the position of blank space in the input string.
	for (int i = 0; i < sentence.length; i++) {
	    if (sentence[i] == ' ') {
		blankposlist[k++] = i;
	    }
	}
	blankposlist[k] = sentence.length;
	// reverse the input string
	reverseString(sentence, 0, sentence.length - 1);

	// Reverse each word
	for (int m = 0; m < sentence.length;) {
	    int reverselen = blankposlist[k] - blankposlist[k - 1] - 1;
	    reverseString(sentence, m, m + reverselen - 1);
	    m = m + reverselen + 1;
	    k--;
	}

	displayArray(sentence);
    }

 public void reverseString(char[] inarray, int start, int end) {
	char ch;
	for (int i = 0; i <= (end - start) / 2; i++) {
	    ch = inarray[start + i];
	    inarray[start + i] = inarray[end - i];
	    inarray[end - i] = ch;
	}
    }

void displayArray(char[] inarray) {
		System.out.println("\n---- Displaying array ---");
		for (char element : inarray) {
			System.out.print(element);
		}
	}

- Rudra April 12, 2013 | Flag Reply
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0
of 0 vote

public class StrRev {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		String sentence = "God is Great";
		StringBuffer sbuf = new StringBuffer();
		String[] s = sentence.split(" ");
		for(int i=0; i<s.length; i++)
		{
			sbuf.append(s[s.length-i-1]).append(" ");
		}
			System.out.println("str buf = " + sbuf);
	}

}

- Guest April 12, 2013 | Flag Reply
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0
of 0 vote

public static void revString(String str){
		 
		 StringBuffer sb = new StringBuffer();
		 String s[] = str.split(" ");
		 int len = s.length;
		 
		 for(int i=0; i< len; i++)
		 {
			 sb.append(s[len-i-1]);
			 if(i!=len-1)
			 {
				 sb.append(" ");
			 }
			 
		 }
		 
		 System.out.println(sb);		 
		 
	 }

- Anonymous April 14, 2013 | Flag Reply
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0
of 0 vote

Guys,
I forgot to mention that I was supposed to use any "in-built String functions such as String.split(), String.Reverse(),etc"

- xankar April 14, 2013 | Flag Reply
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0
of 0 vote

"Sathyaa blackhat" has the answer here:

stackoverflow.com/questions/4705069/c-program-on-reversing-a-sentence

Steps
1) Create a Reverse(start,end) method which reverses chars from start to end.
2) Then do Reverse (start, strlen-1). Reverse the whole string.
3) Then Reverse words by adjusting pointers until you encounter " ".

- xankar April 14, 2013 | Flag Reply
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0
of 0 vote

String a = ActualStringValues;
String[] s = a.split(" ");
a = "" ;
for(String tmp : s){
a = tmp + " " + a;
}
a = a.trim();
System.out.println(a);

- Harish Arora May 02, 2013 | Flag Reply
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0
of 0 votes

Nice. Simplest java approach.

- Kb June 20, 2013 | Flag
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0
of 0 vote

#include <stdio.h>
#include <string.h>


int main()
{
char str[] = "Today is wednesday";
char * temp;
char * revStr[5] = {NULL};
int strCnt = 0;

temp = strtok(str," ");

while(temp)
{
revStr[strCnt] = temp;
strCnt++;
temp = strtok(NULL," ");
}

while(strCnt--)
{
printf("%s ",revStr[strCnt]);
// strCnt--;
}

return 0;
}

- Anonymous June 04, 2013 | Flag Reply
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0
of 0 vote

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
int main()
{
int i,j=0,k=0;
char sent[100],sent2[10][10];
gets(sent);
for(i=0;sent[i]!='\0';i++)
{

if(sent[i] == ' ')
{
sent2[j][k] = '\0';j++;k = 0;i++;
}
sent2[j][k] = sent[i];
k++;
}
sent2[j][k] = '\0';i=0;
for(k=j;k>=0;k--)
{
while(1)
{
if(sent2[k][i] == '\0')
{
printf(" ");i=0;break;
}
printf("%c",sent2[k][i]);i++;
}
}

}

- Anonymous June 16, 2013 | Flag Reply
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0
of 0 vote

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
int main()
{
	int i,j=0,k=0;
	char sent[100],sent2[10][10];
	gets(sent);
	for(i=0;sent[i]!='\0';i++)
	{
		
		if(sent[i] == ' ')
		{
			sent2[j][k] = '\0';j++;k = 0;i++;
		}	
		sent2[j][k] = sent[i];
		k++;
	}
	sent2[j][k] = '\0';i=0;
	for(k=j;k>=0;k--)
	{
		while(1)
		{
			if(sent2[k][i] == '\0')
			{	
				printf(" ");i=0;break;
			}
			printf("%c",sent2[k][i]);i++;
		}				
	}
	
}

- Anonymous June 16, 2013 | Flag Reply
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0
of 0 vote

{
String str= " REVERSE THE STRING";

int lenght=str.length();
int subsi=0;
StringBuilder strB= new StringBuilder();
for (int i= lenght-1; i>=0;i--){

subsi++;
if(str.charAt(i)==' '){
String subs=str.substring(i,i+subsi );
strB.append(subs);
subsi=0;
}
}
}

- Lokesh Chouhan June 27, 2013 | Flag Reply
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0
of 0 vote

public static void main(String[] args) {
		String input = "Today is Wednesday";
		String output = "";
		String[] st = input.split(" ");
		for(int i = st.length; i>0; i--) {
			output += st[i-1] + " ";
		}
		System.out.println(output);
	}

- King007 June 27, 2013 | Flag Reply
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0
of 0 vote

/*Write a program to reverse the sequence of words in a sentence. 

	For Eg: 
	String str = "Today is Wednesday"; 

	Output: 
	String str2 = "Wednesday is Today"*/
	public static String reverse(String s){
		//Step 1 do the null check
		// Step 2 empty string "". is handeled
		String [] str = s.split(" "); 
		String result =""; 
		for(int j=str.length-1;j>=0;j--){
			if(j!=0)
			result += str[j]+" ";
			else
			result += str[j];
		}
		return result;
	}

- Malleswara Dyamappa July 10, 2013 | Flag Reply
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0
of 0 vote

//Working C++ Code

void ReverseWords(char word[] )
{
int counter=0;
int counter_space = 0 ;
int counter_laenge=0;
int zeiger = 0 ;
char arr [10];
bool index = false ;
int k = 0 ;
int length = 0;

for(int i = 0 ; word[i];i++) counter_laenge ++;
for(int i = 0 ; word[i];i++)
{
if(word[i] == 32) counter ++;
}

for(int t = 0; t<counter ; t++)
{

for(int j= 0 ; word[j];j++)
{
if(!index)
{
if(word[j] == 32 ) counter_space ++;
if(counter_space == counter )
{
index = true;
}
}
else
{
arr[k] = word[j];
k++;
length++;
}
}

arr[k] = 0;

//Shift takes place here
for( int r = counter_laenge; r > length+zeiger; r--)
{
word[r-1] = word[r-length-2];
}

for( int l=zeiger,z=0; arr[z];z++,zeiger++)
{
word[zeiger] = arr[z];
}

word[zeiger] = 32;
zeiger++;
index = false;
length = 0;
k=0;
counter_space=0;
}
}

- Schedl July 18, 2013 | Flag Reply
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0
of 0 vote

import java.util.*;

public class ReverseWords {

	public static String reverseWords(String input){
		List<String> out = Arrays.asList(input.split(" "));
		Collections.reverse(out);
		StringBuffer output = new StringBuffer();
		for (String s : out){
			output.append(s + " ");
		}
		return output.toString();
	}
	public static void main(String[] args) {
		System.out.println(ReverseWords.reverseWords("Today is Wednesday"));
	}

}

- Anonymous September 14, 2013 | Flag Reply
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0
of 0 vote

#include <iostream>
#include <stdio.h>

using namespace std;

void doReverse(char *pszStr, int sIdx, int eIdx) {
	while (sIdx < eIdx) {
		char cTmp = pszStr[sIdx];
		pszStr[sIdx] = pszStr[eIdx];
		pszStr[eIdx] = cTmp;
		sIdx++; eIdx--;
	}
}

void doReverseOfSentence(char * csMsg) {
	int nLen = strlen(csMsg);
	doReverse(csMsg, 0, nLen - 1);

	int i = 0, sIdx = 0;
	while (i <= nLen) {
		if (csMsg[i] == ' ' || csMsg[i] == '\0') {
			doReverse(csMsg, sIdx, i - 1);
			sIdx = i + 1;
		}
		i++;
	}
}

int main() {
	char csMsg[] = "Today is Saturday";

	cout << "original string: " << csMsg << endl;
	doReverseOfSentence(csMsg);
	cout << "afterwarth string: " << csMsg << endl;
	getchar();
	return 0;
}

- Passerby_A February 22, 2014 | Flag Reply
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0
of 0 vote

In C# we can do this

var converse="Today is wednesday";
			
		for(int i=converse.Split(' ').Length-1;i>=0;i--)
		{
			Console.Write(converse.Split(' ')[i].ToString().Insert(0," "));
			
		}

- smartaquarius September 06, 2014 | Flag Reply
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0
of 0 vote

reverse words in a string :writeulearn.com/reverse-words-string-donot-reverse-word-letters/

- Anonymous January 10, 2015 | Flag Reply
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0
of 0 vote

reverse words in a string :writeulearn.com/reverse-words-string-donot-reverse-word-letters/

- bhupesh January 10, 2015 | Flag Reply
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0
of 0 vote

reverse words in a string :writeulearn.com/reverse-words-string-donot-reverse-word-letters/

- bhupesh January 10, 2015 | Flag Reply
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0
of 0 vote

reverse words in a string :writeulearn.com/reverse-words-string-donot-reverse-word-letters/

- bhupesh January 10, 2015 | Flag Reply
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0
of 0 vote

public static void reverseStatement(String s){
String a[] = s.split(" ");
int l=0;
int h = a.length-1;
while(l<h){
String temp = a[h];
a[h] = a[l];
a[l]=temp;
l++;
h--;
}
}

- rathor.rajeev August 20, 2016 | Flag Reply


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