Javascript程序反转给定字符串中的单词

示例：让输入字符串为“我非常喜欢这个程序”。该函数应将字符串更改为“much very program this like i”

例子：

Input: s = “geeks quiz practice code” 
Output: s = “code practice quiz geeks”

Input: s = “getting good at coding needs a lot of practice” 
Output: s = “practice of lot a needs coding at good getting”

算法：

• 最初，将给定字符串的单个单词逐个反转，对于上面的示例，在反转单个单词之后，字符串应该是“i ekil siht margorp yrev hcum”。
• 在上面的示例中，从头到尾反转整个字符串以获得所需的输出“much very program this like i”。

下面是上述方法的实现：

Javascript

// Javascript program to reverse 
// a String
      
// Reverse the letters of 
// the word 
function reverse(str, start, end)
{
    // Temporary variable to 
    // store character 
    let temp;        
          
    while (start <= end) 
    {
        // Swapping the first and 
        // last character 
        temp = str[start];
        str[start] = str[end];
        str[end] = temp;
        start++;
        end--;
    }
}
      
// Function to reverse words
function reverseWords(s)
{
    // Reversing individual words as
    // explained in the first step
    s = s.split("");
    let start = 0;
    for (let end = 0; 
             end < s.length; end++) 
    {
        // If we see a space, we reverse 
        // the previous word (word between 
        // the indexes start and end-1 
        // i.e., s[start..end-1]
        if (s[end] == ' ') 
        {
            reverse(s, start, end);
            start = end + 1;
        }
    }
    // Reverse the last word
    reverse(s, start, s.length - 1);
          
    // Reverse the entire String
    reverse(s, 0, s.length - 1);
    return s.join("");
}
      
// Driver Code
var s = 
"i like this program very much ";
      
document.write(reverseWords(s));
// This code is contributed by avanitrachhadiya2155

输出：

much very program this like i

另一种方法：

我们可以通过以相反的方式拆分和保存字符串来完成上述任务。

下面是上述方法的实现：

Javascript

// JavaScript program to reverse a string
var s = ["i", "like", "this", 
         "program", "very", "much"];
                                          
var ans ="";
for (var i = 5; i >= 0; i--)
{
    ans += s[i] + " ";
}
document.write(
"Reversed String:"+ "<br>");
document.write(
ans.slice(0,ans.length-1));

输出：

Reversed String:
much very program this like i

时间复杂度： O(n)

不使用任何额外空间：
上面的任务也可以通过从中间开始拆分和直接交换字符串来完成。由于涉及直接交换，因此消耗的空间也更少。

下面是上述方法的实现：

Javascript

// Javascript code to reverse a string
  
// Reverse the string
function RevString(s, l)
{    
    // Check if number of words 
    // is even
    if (l % 2 == 0)
    {
        // Find the middle word
        let j = parseInt(l / 2, 10);
  
        // Starting from the middle start
        // swapping words at jth position 
        // and l-1-j position
        while (j <= l - 1)
        {
            let temp;
            temp = s[l - j - 1];
            s[l - j - 1] = s[j];
            s[j] = temp;
            j += 1;
        }
    }
  
    // Check if number of words is odd
    else
    {
        // Find the middle word
        let j = parseInt((l / 2), 10) + 1;
  
        // Starting from the middle start
        // swapping the words at jth
        // position and l-1-j position
        while (j <= l - 1)
        {
            let temp;
            temp = s[l - j - 1];
            s[l - j - 1] = s[j];
            s[j] = temp;
            j += 1;
        }
    }
  
    let S = s[0];
  
    // Return the reversed sentence
    for(let i = 1; i < 9; i++)
    {
        S = S + " " + s[i];
    }
    return S;
}
  
// Driver code
let s = "getting good at coding "
        "needs a lot of practice";
              
let words = ["getting", "good", "at",
             "coding", "needs", "a",
             "lot", "of", "practice"];
document.write(RevString(words, 9));
  
// This code is contributed by suresh07

输出：

practice of lot a needs coding at good getting

有关详细信息，请参阅有关给定字符串中的反向单词的完整文章！