以相反的顺序打印字符串的单词

让一个字符串说“我是一个极客”。所以，输出应该是“GEEK A AM I”。这可以通过多种方式完成。解决方案之一在字符串中的反向单词中给出。

例子：

Input : I AM A GEEK
Output : GEEK A AM I

Input : GfG IS THE BEST
Output : BEST THE IS GfG

这可以通过使用“ %s 格式说明符”的属性以更简单的方式完成。
属性：%s 将获取所有值，直到它变为 NULL 即 '\0'。

示例：char String[] = “I AM A GEEK” 存储如下图所示：

方法：从最后一个字符开始遍历字符串，向第一个字符移动。遍历时，如果遇到空格字符，则在该位置放置一个 NULL 并在 NULL字符之后打印剩余的字符串。重复此操作，直到循环结束，当循环结束时，打印字符串，%s 将打印字符，直到遇到第一个 NULL字符。

让我们在图表的帮助下查看该方法：
step 1：从最后一个字符开始遍历，直到遇到空格字符。

步骤 2：在空格字符的位置放置一个 NULL字符并打印其后的字符串。

步骤3：最后，循环到达第一个字符时结束，所以打印剩余的字符，它将打印第一个NULL字符，因此将打印第一个单词。

C++

// C++ program to print reverse
// of words in a string.
#include 
 
using namespace std;
 
string wordReverse(string str)
{
    int i = str.length() - 1;
    int start, end = i + 1;
    string result = "";
 
    while (i >= 0) {
        if (str[i] == ' ') {
            start = i + 1;
            while (start != end)
                result += str[start++];
 
            result += ' ';
 
            end = i;
        }
        i--;
    }
    start = 0;
    while (start != end)
        result += str[start++];
 
    return result;
}
 
// Driver code
int main()
{
    string str = "I AM A GEEK";
 
    cout << wordReverse(str);
 
    return 0;
}
 
// This code is contributed
// by Imam

C

// C program to print reverse of words in
// a string.
#include 
#include 
 
void printReverse(char str[])
{
    int length = strlen(str);
 
    // Traverse string from end
    int i;
    for (i = length - 1; i >= 0; i--) {
        if (str[i] == ' ') {
 
            // putting the NULL character at the
            // position of space characters for
            // next iteration.
            str[i] = '\0';
 
            // Start from next character
            printf("%s ", &(str[i]) + 1);
        }
    }
 
    // printing the last word
    printf("%s", str);
}
 
// Driver code
int main()
{
    char str[] = "I AM A GEEK";
    printReverse(str);
    return 0;
}

Java

// Java program to print reverse
// of words in a string.
import java.io.*;
import java.lang.*;
import java.util.*;
 
class GFG {
    static String wordReverse(String str)
    {
        int i = str.length() - 1;
        int start, end = i + 1;
        String result = "";
 
        while (i >= 0) {
            if (str.charAt(i) == ' ') {
                start = i + 1;
                while (start != end)
                    result += str.charAt(start++);
 
                result += ' ';
 
                end = i;
            }
            i--;
        }
 
        start = 0;
        while (start != end)
            result += str.charAt(start++);
 
        return result;
    }
 
    // Driver code
    public static void main(String[] args)
    {
        String str = "I AM A GEEK";
 
        System.out.print(wordReverse(str));
    }
}
 
// This code is contributed
// by Akanksha Rai(Abby_akku)

Python3

# Python3 program to print reverse
# of words in a string.
 
 
def wordReverse(str):
    i = len(str)-1
    start = end = i+1
    result = ''
 
    while i >= 0:
        if str[i] == ' ':
            start = i+1
            while start != end:
                result += str[start]
                start += 1
            result += ' '
            end = i
        i -= 1
    start = 0
    while start != end:
        result += str[start]
        start += 1
    return result
 
 
# Driver Code
str = 'I AM A GEEK'
print(wordReverse(str))
 
# This code is contributed
# by SamyuktaSHegde

C#

// C# program to print reverse
// of words in a string.
using System;
class GFG {
    static String wordReverse(String str)
    {
        int i = str.Length - 1;
        int start, end = i + 1;
        String result = "";
 
        while (i >= 0) {
            if (str[i] == ' ') {
                start = i + 1;
                while (start != end)
                    result += str[start++];
 
                result += ' ';
 
                end = i;
            }
            i--;
        }
 
        start = 0;
        while (start != end)
            result += str[start++];
 
        return result;
    }
 
    // Driver code
    public static void Main()
    {
        String str = "I AM A GEEK";
 
        Console.Write(wordReverse(str));
    }
}
 
// This code is contributed
// by Akanksha Rai(Abby_akku)

PHP

= 0)
    {
        if($str[$i] == ' ')
        {
            $start = $i + 1;
            while($start != $end)
                $result = $result . $str[$start++];
             
            $result = $result . ' ';
             
            $end = $i;
        }
        $i--;
    }
    $start = 0;
    while($start != $end)
        $result = $result . $str[$start++];
     
    return $result;
}
 
// Driver code
$str = "I AM A GEEK";
echo wordReverse($str);
 
// This code is contributed by ita_c
?>

Javascript

 
// Javascript program to print reverse
// of words in a string.
function wordReverse(str)
{
    var i = str.length - 1;
    var start, end = i + 1;
    var result = "";
     
    while (i >= 0)
    {
        if (str[i] == ' ')
        {
            start = i + 1;
            while (start != end)
                result += str[start++];
             
            result += ' ';
            end = i;
        }
        i--;
    }
    start = 0;
     
    while (start != end)
        result += str[start++];
     
    return result;
}
 
// Driver code
var str = "I AM A GEEK";
 
document.write(wordReverse(str));
 
// This code is contributed by rutvik_56
 

输出：

GEEK A AM I

时间复杂度： O(len(str))

辅助空间： O(len(str))

不使用任何额外空间：

遍历字符串并镜像字符串中的每个单词，然后在最后镜像整个字符串。

以下 C++ 代码可以处理多个连续空格。

C++

#include 
#include 
#include 
 
using namespace std;
 
string reverse_words(string s)
{
    int left = 0, i = 0, n = s.size();
   
    while (s[i] == ' ')
        i++;
   
    left = i;
   
    while (i < n)
    {
        if (i + 1 == n || s[i] == ' ')
        {
            int j = i - 1;
            if (i + 1 == n)
                j++;
           
            while (left < j)
                swap(s[left++], s[j--]);
           
            left = i + 1;
        }
        if (s[left] == ' ' && i > left)
            left = i;
       
        i++;
    }
    //reverse(s.begin(), s.end());
    return s;
}
 
int main()
{
 
    string str = "I AM A GEEK";
 
    str = reverse_words(str);
 
    cout << str;
   
    return 0;
  // This code is contributed
  // by Gatea David
}

Javascript

 
// JavaScript code for the approach
 
function reverse_words(s)
{
    let left = 0, i = 0, n = s.length;
 
    while (s[i] == ' ')
        i++;
 
    left = i;
 
    while (i < n)
    {
        if (i + 1 == n || s[i] == ' ')
        {
            let j = i - 1;
            if (i + 1 == n)
                j++;
            let temp;
            let a = s.split("");
            while (left < j){
                temp = a[left];
                a[left] = a[j];
                a[j] = temp;
                left++;
                j--;
            }
            s = a.join("");
         
            left = i + 1;
        }
        if (s[left] == ' ' && i > left)
            left = i;
     
        i++;
    }
    s = s.split('').reverse().join('');
    return s;
}
 
// driver code
 
let str = "I AM A GEEK";
 
str = reverse_words(str);
 
document.write(str);
 
// This code is contributed by shinjanpatra
 

输出：

GEEK A AM I

时间复杂度： O(len(str))

辅助空间： O(1)