CareerCup

private static void reverse(char[] c) {
		reverse(c,0,c.length-1);
		
		int wordStart=0;
		for(int i=0;i<c.length;i++)
		{
			if(c[i]==' ')
			{
				reverse(c,wordStart,i-1);
				wordStart=i+1;
			}
			else if(i==c.length-1)
			{
				reverse(c,wordStart,i);
			}
		}
	}

	private static void reverse(char[] c, int i, int j) {
		if(i>=j)
			return;
		for(int k=i;k<=(i+j)/2;k++)
		{
			char temp=c[k];
			c[k]=c[i+j-k];
			c[i+j-k]=temp;
		}
	}

void wordrev(char * str) {
  char * last = str;
  char * ptr = str;
  strrev( str );
  while( *ptr != 0 ) {
     if ( *ptr == ' ' ) {
        *ptr = '\0';
        strrev( last );
        *ptr = ' ';
        last = ptr + 1;
     }
     ptr++;
  }
  strrev(last);  
  return;
}

void strrev(char * str) {
  int len = strlen(str);
  int len_2 = len / 2;
  char temp;
  int i;
  for(i = 0; i < len_2;i++) {
     temp = str[i];
     str[i] = str[len-i-1];
     str[len-i-1] = temp;    
  }
  return;
}

#include <stdio.h>

char sentence[] = "This is my big beautiful sentence having multiple words";

void reverse(char *s)
{
    char *tmp = s;

    while(s && *s && *s != ' ')
	s++;
    if(*s == ' ') {
	*s = '\0';
	reverse(++s);
    }
    printf("%s ",tmp);
}


int main(void)
{
    reverse(sentence);
    printf("\n");

    return 0;
}

In C# its easy
Take the sentence into string.Then store each word of the string in string array by performing string.split(' ') then apply a decrement loop on this string array and append each word using string builder.

in java, you can use the StringTokenizer class

1 #include <stdio.h>
  2 #include <string.h>
  3 #include <stdlib.h>
  4 
  5 int
  6 main ()
  7 {
  8     char str[] = "This is a nice world";
  9     int len = strlen ( str );
 10     int pos = len;
 11     char *rev = (char *)malloc( len + 1 );
 12     memset ( rev, ' ', len );
 13     rev [len] = '\0';
 14     printf ("rev = X%sX\n", rev );
 15     char *str1 = strtok ( str, " " );
 16     len = strlen ( str1 );
 17     strncpy ( rev + pos - len, str1, len );
 18     pos = pos - len - 1;
 19     while ( (str1 = strtok ( NULL, " " )) != NULL )
 20     {
 21         len = strlen ( str1 );
 22         strncpy ( rev + pos - strlen ( str1 ), str1, strlen (str1));
 23         pos = pos - strlen ( str1 ) - 1;
 24     }
 25 
 26     printf ("rev = %s\n", rev );
 27     free ( rev );
 28     return 0;
 29 }

public static void main(String[] args) {
String s = new String("this is a new world");
String c[] = s.split(" ");
for (int i = c.length -1; i >=0 ; i--){
System.out.print(c[i] + " ");
}
}

If you are not allowed to use any library functions to split the string, nor to create any additional strings and/or arrays, in Java you can do it in O(n) by reversing the whole string first and then reversing the words. Here is a solution:



public class WordReversing {
public static char[] reverse(char[] string) {
reverseChars(string, 0, string.length - 1); // reverse whole string
int wordStart = 0;
int wordEnd;

while (wordStart < string.length) {
// skip multiple spaces and find the next word start position
while (wordStart < string.length && string[wordStart] == ' ') {
wordStart++;
}

wordEnd = wordStart;
while (wordEnd < string.length && string[wordEnd] != ' ') {
wordEnd++;
}
reverseChars(string, wordStart, wordEnd - 1); // reverse the word
wordStart = wordEnd + 1;
}

return string;
}

public static void reverseChars(char[] string, int from, int to) {
if (from < 0 || to >= string.length || from >= to) {
return;
}
while (from < to) {
char temp = string[from];
string[from] = string[to];
string[to] = temp;
from++;
to--;
}
}

public static void main(String[] args) {
char[] s = " This is a test. ".toCharArray();
System.out.println(reverse(s));
}
}

<pre lang="java" line="1" title="CodeMonkey75291" class="run-this">public class WordReversing {
public static char[] reverse(char[] string) {
reverseChars(string, 0, string.length - 1); // reverse whole string
int wordStart = 0;
int wordEnd;

while (wordStart < string.length) {
// skip multiple spaces and find the next word start position
while (wordStart < string.length && string[wordStart] == ' ') {
wordStart++;
}

wordEnd = wordStart;
while (wordEnd < string.length && string[wordEnd] != ' ') {
wordEnd++;
}
reverseChars(string, wordStart, wordEnd - 1); // reverse the word
wordStart = wordEnd + 1;
}

return string;
}

public static void reverseChars(char[] string, int from, int to) {
if (from < 0 || to >= string.length || from >= to) {
return;
}
while (from < to) {
char temp = string[from];
string[from] = string[to];
string[to] = temp;
from++;
to--;
}
}

public static void main(String[] args) {
char[] s = " This is a test. ".toCharArray();
System.out.println(reverse(s));
}
}
</pre><pre title="CodeMonkey75291" input="yes">
</pre>

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

using namespace std;

void reverseString(char* input, int start, int end)
{
if (end - start == 0)
{
return;
}
else if (end - start == 1)
{
char temp = input[start];
char temp2 = input[end];

input[start] = temp2;
input[end] = temp;
return;
}

for(int i = start ; i <= start + (end-start)/2 ; i++)
{
//printf("\r\n swapping %d and %d",i , (start + end - i));
char temp = input[i];
char temp2 = input[start + end - i];

input[i] = temp2;
input[start + end - i] = temp;
}
}

void reverseWords(char* input, int length)
{
int start = 0;
for(int i = 0 ; i <= length ; i++)
{
if (input[i] == ' ' || input[i] == '\0')
{
reverseString(input, start, i-1);
start = i + 1;
}
}

reverseString(input,0, length-1);
}

C code:

int main()
{
	char buffer[] = "this is the best problem";
	int i = strlen(buffer);
	int j = i;

	while(j > 0) {
		char ch = buffer[j];
		if(ch == ' ') {
			i = j + 1;
			printf("%s \n", buffer + i);
			buffer[i] = 0;
		}
		--j;
	}

	printf("%s \n", buffer);
	return 0;
}

String reverse(String myString)
{
    StringBuilder sb = new StringBuilder(myString);
    String rev=sb.toString();
    StringTokenizer st = new StringTokenizer(rev);
    sb.delete(0,sb.length());
    while(st.hasMoreTokens())
    {
    sb.append(new StringBuilder(st.hasMoreTokens).reverse());
    sb.append(" ");
    }
       return sb.toString();
}

String[] words = sentence.split(" ");
Collections.reverse(Arrays.asList(words));
                
StringBuffer sbuffer = new StringBuffer();
for (String str : words) {
    sbuffer.append(str + " ");
}

return sbuffer.toString();

In javascript you can do it in 1 line,

var original = 'Hello World';
var reversed = original.split(' ').reverse().join(' ');

private static String swap(String stringToSwap) {
String[] arr = testStr.split(" ");
int endIndex = arr.length - 1;
int j = endIndex;
String temp = "";
for (int i = 0; i < endIndex / 2; i ++){
temp = arr[i];
arr[i] = arr[j];
arr[j] = temp;
j --;
}
StringBuilder sb = new StringBuilder();
for(int k = 0; k < arr.length; k ++){
sb.append(arr[k]);
sb.append(" ");
}
return sb.toString();
}

#using PERL

$input="Wednesday is great day";
@inpuarr=split(" ",$input);
@newoutarr=reverse(@inpuarr);
for ($i=0;$i<scalar(@newoutarr);$i++)
{ print "$newoutarr[$i]","\n";}

reverse_string(char  *str)
{
  char  ch, *str1 = str+((strlen(str))-1);

  if(!str)
    return;

  while(str<str1)
  {
    ch = *str;
    *str = *str1;
    *str1 = ch;
    str++; str1--;    
  }

  return;
}