Interview Question


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1
of 1 vote

public static void main(String[] args) {
		System.out.println(reverse("1+2*3-204"));
	}

	/**
	 * Reverse this string 1+2*3-20. Note: 20 must be retained as is. Expected
	 * output: 20-3*2+1
	 */
	public static String reverse(String str) {

		char[] c = str.toCharArray();

		int i = 0;
		Stack<String> st = new Stack<String>();
		while (i < c.length) {
			String t = "";
			while (!st.isEmpty() && isN(st.peek()) && isN(String.valueOf(c[i]))) {
				String k = st.pop();
				t = k + t;
			}
			t += String.valueOf(c[i]);
			st.push(String.valueOf(t));
			i++;
		}

		String ret = "";
		while (!st.isEmpty())
			ret += st.pop();
		return ret;
	}

	public static boolean isN(String str) {
		boolean f = true;
		try {
			Integer.parseInt(str);
		} catch (Exception e) {
			f = false;
		}
		return f;
	}

- sudip.innovates September 22, 2017 | Flag Reply
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1
of 1 vote

class ReverseString {
public static void main(String[] args) {
String input = "1+2*3-20";

// getBytes() method to convert string
// into bytes[].
byte[] strAsByteArray = input.getBytes();

byte[] result = new byte[strAsByteArray.length];


// Store result in reverse order into the
// result byte[]
for (int i = 0; i < strAsByteArray.length; i++){

result[i] = strAsByteArray[strAsByteArray.length - i - 1];

}
byte temp = result[0];
result[0] = result[1];
result[1] = temp;
System.out.println(new String(result));
}
}

- Syam September 30, 2017 | Flag Reply
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0
of 0 vote

/*
Reverse this string 1+2*3-20. Note: 20 must be retained as is.
Expected output: 20-3*2+1
 */
public class ReverseEquation {
    public static void main(String[] args) {
        final String input = "1+2*3-20";
        System.out.println(new ReverseEquation().reverse(input));
        //prints 20-3*2+1

    }

    String reverse(String s) {
        BreakIterator b = java.text.BreakIterator.getWordInstance();
        b.setText(s);
        StringBuilder sb = new StringBuilder();
        for (int end = b.last(), start = b.previous(); start != BreakIterator.DONE;
             end = start, start = b.previous()) {
            String w = s.substring(start, end);
            sb.append(w);
        }
        return sb.toString();
    }

}

- Makarand September 22, 2017 | Flag Reply
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0
of 0 vote

def reverseString(theString):
	operatorList = ['*', '+', '-', '/']
	finalString = ""
	i = len(theString) - 1
	while (i >= 0):
		currentNum = ""
		while (i >= 0 and theString[i] not in operatorList):
			currentNum = theString[i] + currentNum
			i -= 1
		
		totalString += currentNum
		if (i >= 0):
			totalString += theString[i]
		i -= 1

- SK September 22, 2017 | Flag Reply
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0
of 0 vote

def revStr(string):
    newAr = []
    if '20' in string:
        newAr = ['20']
        string = string.replace('20','')
    else:
        newAr = newAr
    i = len(string) - 1
    while i >= 0:
        newAr.append(string[i])
        print(string[i])
        i = i -1
    return(''.join(newAr))

- sulabhchaturvedi08 September 23, 2017 | Flag Reply
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0
of 0 vote

void ReverseExpression(string &s)
{
	reverse(s.begin(), s.end());
	int start = -1;
	for (int i = 0; i < s.size(); ++i) {
		if (isdigit(s[i])) {
			if (start == -1) {
				start = i;
			}
			if (i + 1 == s.size() ||
				!isdigit(s[i + 1]))
			{
				reverse(s.begin() + start, s.begin() + i + 1);
				start = -1;
			}
		}
	}
}

- Alex September 26, 2017 | Flag Reply
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0
of 0 vote

package string;

import java.util.Scanner;

public class ReverseExp {

public static String reverExp(String s)
{
char[] ch=s.toCharArray();
String res="";int k=0;
for (int i = ch.length-1 ; i >= 0; i--) {
int start=i;
while(i>=0 && ch[i] >=48 && ch[i] <= 57)
{
i--;
}
int end=i+1;

while(end <= start)
{
res=res+ch[end];
end++;
}
if(i>=0) {
res=res+ch[i];}
}
return res;
}
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
System.out.println("Enter the String: ");
String s=sc.nextLine();
s=reverExp(s);
System.out.println("Reverse of expression: "+s);
}

}

- Anonymous October 22, 2017 | Flag Reply
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0
of 0 vote

package string;

import java.util.Scanner;

public class ReverseExp {

	public static String reverExp(String s)
	{
		char[] ch=s.toCharArray();
		String res="";int k=0;
		for (int i = ch.length-1 ; i >= 0; i--) {
			int start=i;
			while(i>=0 && ch[i] >=48 && ch[i] <= 57)
			{
				i--;
			}
			int end=i+1;
			
			while(end <= start)
			{
				res=res+ch[end];
				end++;
			}
			if(i>=0) {
			res=res+ch[i];}
		}
		return res;
	}
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		System.out.println("Enter the String: ");
		String s=sc.nextLine();
		s=reverExp(s);
		System.out.println("Reverse of expression: "+s);
	}

}

- Sachin M October 22, 2017 | Flag Reply
Comment hidden because of low score. Click to expand.
0
of 0 vote

package string;

import java.util.Scanner;

public class ReverseExp {

	public static String reverExp(String s)
	{
		char[] ch=s.toCharArray();
		String res="";int k=0;
		for (int i = ch.length-1 ; i >= 0; i--) {
			int start=i;
			while(i>=0 && ch[i] >=48 && ch[i] <= 57)
			{
				i--;
			}
			int end=i+1;
			
			while(end <= start)
			{
				res=res+ch[end];
				end++;
			}
			if(i>=0) {
			res=res+ch[i];}
		}
		return res;
	}
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		System.out.println("Enter the String: ");
		String s=sc.nextLine();
		s=reverExp(s);
		System.out.println("Reverse of expression: "+s);
	}

}

- Sachin M October 22, 2017 | Flag Reply
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0
of 0 vote

package string;

import java.util.Scanner;

public class ReverseExp {

	public static String reverExp(String s)
	{
		char[] ch=s.toCharArray();
		String res="";int k=0;
		for (int i = ch.length-1 ; i >= 0; i--) {
			int start=i;
			while(i>=0 && ch[i] >=48 && ch[i] <= 57)
			{
				i--;
			}
			int end=i+1;
			
			while(end <= start)
			{
				res=res+ch[end];
				end++;
			}
			if(i>=0) {
			res=res+ch[i];}
		}
		return res;
	}
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		System.out.println("Enter the String: ");
		String s=sc.nextLine();
		s=reverExp(s);
		System.out.println("Reverse of expression: "+s);
	}

}

- Sachin M October 22, 2017 | Flag Reply
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0
of 0 vote

var string2 = "1+2*3-20";
var sliceout1= string2.slice(0,6);
var sliceout2= string2.slice(6);


var splitString1= sliceout1.split("");
splitString1.push(sliceout2);

var reverseArray= splitString1.reverse();
console.log(reverseArray);

reverseArray.toString();

console.log("The reversed string is: "+reverseArray);

- Jessica Erazo November 01, 2017 | Flag Reply
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0
of 0 vote

var string2 = "1+2*3-20";
var sliceout1= string2.slice(0,6);
var sliceout2= string2.slice(6);


var splitString1= sliceout1.split("");
splitString1.push(sliceout2);

var reverseArray= splitString1.reverse();
console.log(reverseArray);

reverseArray.toString();

console.log("The reversed string is: "+reverseArray);

- Jessica Erazo November 01, 2017 | Flag Reply
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0
of 0 vote

#generic solution
def reverseString(str1):
lst_str = []
str2 = ''
str3 = ''
str_flag = 0
sy_flag = 0
for i in str1:
if i.isdigit():
if sy_flag == 1:
lst_str.append(str2)
str2 = ''
sy_flag = 0
str2 = str2 + i
str_flag = 1
else:
if str_flag == 1:
lst_str.append(str2)
str2 = ''
str_flag = 0
str2 = i + str2
sy_flag = 1
lst_str.append(str2)
for j in reversed(lst_str):
str3 = str3 + j
return str3

str1 = '1+2*3-20'
print reverseString(str1)
#below one is more generic
str1 = '-41+2**36-20/+6*'
print reverseString(str1)

- RakeshSharma November 03, 2017 | Flag Reply
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0
of 0 vote

#generic solution
def reverseString(str1):
    lst_str = []
    str2 = ''
    str3 = ''
    str_flag = 0
    sy_flag = 0
    for i in str1:
        if i.isdigit():
            if sy_flag == 1:
                lst_str.append(str2)
                str2 = ''
                sy_flag = 0
            str2 = str2 + i    
            str_flag = 1
        else:        
            if str_flag == 1:
                lst_str.append(str2)
                str2 = ''
                str_flag = 0
            str2 = i + str2    
            sy_flag = 1                
    lst_str.append(str2)          
    for j in reversed(lst_str):
        str3 = str3 + j 
    return str3
 
str1 = '1+2*3-20'
print reverseString(str1) 
#below one is more generic   
str1 = '-41+2**36-20/+6*'
print reverseString(str1)

- RakeshSharma November 03, 2017 | Flag Reply
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0
of 0 vote

#include<bits/stdc++.h>
using namespace std;

int main()
{
string str;
getline(cin,str);
string output="";
int j;
for(int i=str.length()-1;i>=-1;i--)
{
if(i==-1 || str[i] == '*' || str[i] == '+' || str[i] == '-' || str[i] == '/')
{
int j = i;
j++;
while(str[j] != '*' && str[j] != '-' && str[j] != '+' && str[j] != '/' && str.length() > j)
{
output = output + str[j];
j++;
}
if(i != -1)
output = output + str[i];
}
}
cout<<output<<endl;


return 0;}

- Shubham Garg December 08, 2017 | Flag Reply
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0
of 0 vote

Reverse the whole string as is. Next reverse the numbers.
Logic remains same as "This is a book" --> "book a is This" excepting , watch out for mathematical operations, as suppose to space.

C Solution:

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

void ReverseStringUtil(char *str,int start,int end)
{
    char temp;
    while(start < end)
    {
        temp = str[start];
        str[start] = str[end];
        str[end] = temp;
        start++;
        end--;
        
    }
}

int main()
{
    char *str = (char *)malloc(100 * sizeof(char));
    int start, end;
    fgets(str,100,stdin);
    str[strlen(str)-1] = '\0';
    printf("Input string is - %s \n", str);
    ReverseStringUtil(str,0,strlen(str)-1);
    printf("Semi Output String is - %s \n", str);
    int i=0;
    while(str[i]!='\0')
    {
        start = i;
        for(; str[i]!='+'&&str[i]!='\0'&&str[i]!='-'&&str[i]!='*'&&str[i]!='/'&&str[i]!='%';i++);
        end = i-1;
        ReverseStringUtil(str,start,end);
        i++;
    }
    
    printf("Output String is %s \n", str);
    return 0;
}

- gairu.hobbies January 22, 2018 | Flag Reply
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0
of 0 vote

def reverse_str(string)
  newString= ""
  strArr   = string.chars
  numArr = string.split(/[-,+,*,\/]/)
  operatorArr = ['*', '+', '-', '/']
  i = strArr.length.to_i - 1
  j = numArr.length.to_i - 1
  
  
  while i >= 0 
   a = strArr[i]  
    if operatorArr.include?(a)
      newString = newString + "#{a}"
     i = i - 1
    else
      b = numArr[j]
      newString = newString + "#{b}"
      j = j -1
      i = i - b.length
   end
  end
  puts newString
end

string = "1+2*3-20"
reverse_str(string)
string2 = "10-2*3-2000"
reverse_str(string2)

string3 = "10-2*3-+5-992000"
reverse_str(string3)

- ShariqueQA January 26, 2018 | Flag Reply
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0
of 0 vote

def reverse_string(string):
    if "20" in string:
        array = ["02"]
        string = string.replace("20", "02")

    return string[::-1]


print(reverse_string("1 + 2 * 3 - 20"))

- Enthrayu January 27, 2018 | Flag Reply
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0
of 0 vote

public class String1 {
    public static void main(String[] args) {

        String1 s = new String1();
        String str = "1+2*3-20";
        String sa[] = str.split("");
        String ss = s.solution(sa);
        System.out.println(ss);
    }

    public String solution(String s[]){
        int l = s.length -1;
        String out="";
        int i=l;
        while(i> -1){
            String c = s[i];
            int j=0;
            if(!c.equals("+") || !c.equals("-") || !c.equals("*")){
                j=i;
            }
            while (j >0){
                String c1 = s[j];
                if(c1.equals("+") || c1.equals("-") || c1.equals("*")){
                    out = out + c1;
                    j = 0;
                }else{
                    out = c1 + out;
                    j--;
                }
                i--;
            }
        }
        return  out;
    }

}

- ss January 29, 2018 | Flag Reply
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0
of 0 vote

public class String1 {
public static void main(String[] args) {

String1 s = new String1();
String str = "1+2*3-20";
String sa[] = str.split("");
String ss = s.solution(sa);
System.out.println(ss);
}

public String solution(String s[]){
int l = s.length -1;
String out="";
int i=l;
while(i> -1){
String c = s[i];
int j=0;
if(!c.equals("+") || !c.equals("-") || !c.equals("*")){
j=i;
}
while (j >0){
String c1 = s[j];
if(c1.equals("+") || c1.equals("-") || c1.equals("*")){
out = out + c1;
j = 0;
}else{
out = c1 + out;
j--;
}
i--;
}
}
return out;
}
}

- ss January 29, 2018 | Flag Reply
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0
of 0 vote

def reverseString(string):
temp = string[-2:]
length = len(string) -2
output = temp + string[5::-1]
print "{} is the actual string and {} is the outcome string".format(string, output)

if __name__ == '__main__':
reverseString("1+2*3-20")

- Dayananda D R February 11, 2018 | Flag Reply
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0
of 0 vote

def reverseString(string):
    temp = string[-2:]
    length = len(string) -2
    output =  temp + string[5::-1]
    print "{} is the actual string and {} is the outcome string".format(string, output)

if __name__ == '__main__':
    reverseString("1+2*3-20")

- Dayananda D R February 11, 2018 | Flag Reply
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0
of 0 vote

var str = "1+2*3-20";
	str.split('').reverse().join('').replace(/02/gi, "20");

- Gopesh February 12, 2018 | Flag Reply
Comment hidden because of low score. Click to expand.
0
of 0 vote

def foo(st):
b='

'
c='

'
for i in st:

- Anonymous February 20, 2018 | Flag Reply
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0
of 0 vote

This is generic to keeping numbers as is and reversing on basis of operators.
1+2*3-20+5325/133

Ans : 133/5325+20-3*2+1

import java.util.ArrayList;
import java.util.HashSet;

public class ReverseStringsKeepNumberAsIs {
	HashSet<String> hs = new HashSet<String>();
	
	ReverseStringsKeepNumberAsIs(){
		this.hs.add("+");
		this.hs.add("-");
		this.hs.add("*");
		this.hs.add("/");
		this.hs.add("%");
		this.hs.add("^");
		this.hs.add("\\");
	}
	
	String reversalNumSame(String str) {
		// 1+2*3-20
		String[] brokenStr = (str+" ").split("");
		// can be used str+"".toCharArray()
                // Space is being used as a end of line character
		String result="",temp="";
		for (String c:brokenStr) {
			if ((this.hs.contains(c)) || (c.equalsIgnoreCase(" "))) {
				result = c + temp + result;
				temp="";
				c = "";
			}
			temp = temp + c;
		}
		return result.trim();
		
	}

- shubhamsrivastava007 February 22, 2018 | Flag Reply
Comment hidden because of low score. Click to expand.
0
of 0 vote

// Javascript Implementation - 

/**
 * Reverse this string 1+2*3-20. Note: 20 must be retained as is. Expected
 * output: 20-3*2+1
 */


function reverseString(str) {
  let startIndex = 0;
  let stack = [];
  for(let i = 0, length = str.length; i < length; i++) {
    const char = str[i];
    if(isNaN(char)){
      let subStr = str.substring(startIndex, i);
      stack.push(subStr);
      stack.push(str[i]);
      startIndex = i+1;
    }
  }
  if(startIndex < str.length){
    let subStr = str.substring(startIndex);
    stack.push(subStr);
  }
  return stack.reverse().join('');
}

const str = "1+2*3-20+2000+";
console.log("Before Reverse String is -> " +  str);
const reverseStr = reverseString(str);
console.log("After  Reverse String is -> " +  reverseStr);

- Amit Bansal March 06, 2018 | Flag Reply
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0
of 0 vote

a = '221*3+1-23'

i = len(a) - 1
j = len(a) - 1

b = []

while i > 0:
if a[i] not in ('*', '+', '-', '/'):
i -= 1
else:
b.append(a[i + 1:j + 1])
b.append(a[i])
i -= 1
j = i

b.append(a[i:j + 1])

print(str(b))

- Anonymous March 31, 2018 | Flag Reply
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0
of 0 vote

def reverse_arith_string(str_arith):
    '''
    Input Arithmetic operations and  numbers as strings and reverse the string
    without reversing values
    Time complexity = O(N) - Linearily Traversing in string
    Space complexity = O(N) - as storing the reversed string
    
    '''
    
    str_arith = str_arith.strip() 
    if str_arith == "" : return None
    
    d_sym={'+':0,'*':0,'-':0}
    str_arith_rev = ''
    end_pos = len(str_arith)

    for start_pos in range(len(str_arith)-1,-1,-1):
        if str_arith[start_pos] in d_sym : 
           str_arith_rev = str_arith_rev + str_arith[start_pos + 1:end_pos] + str_arith[start_pos]
           end_pos = start_pos
    str_arith_rev = str_arith_rev + str_arith[0:end_pos]

    return str_arith_rev

print(reverse_arith_string(" 1+2*3-20 "))
print(reverse_arith_string("1+2*3-204"))
print(reverse_arith_string("1+2*3-0"))
print(reverse_arith_string(""))

- Sri May 25, 2018 | Flag Reply
Comment hidden because of low score. Click to expand.
0
of 0 vote

public class SplitRev 
{
	public static void main(String[] args) 
	{
		String s="1+2*3-204";
		String no[]=s.split("[^0-9]");
		String del[]=s.split("[0-9]");
		String tot[]=new String[no.length+del.length];
		int k=no.length-1,l=del.length-1;
		for(int i=0;i<tot.length;i++)
		{
			int j=i+1;
			if(!(j%2==0))
			{
				tot[i]=no[k];
				k--;
			}
			else
			{
				tot[i]=del[l];
				l--;
			}
		}
		String revSt="";
		for(String st: tot)
			revSt+=st;
		System.out.println(revSt);
	}

.

- Jai July 16, 2018 | Flag Reply


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