字符串中最后一个单词的长度

给定一个由大写/小写字母和空格字符' ' 组成的字符串s，返回字符串中最后一个单词的长度。如果最后一个单词不存在，则返回 0。

例子：

Input  : str = "Geeks For Geeks"
Output : 5
length(Geeks)= 5

Input : str = "Start Coding Here"
Output : 4
length(Here) = 4

Input  :  **
Output : 0

方法 1：从索引 0 迭代字符串
如果我们从左到右迭代字符串，我们必须注意最后一个单词后面的空格。第一个单词之前的空格很容易被忽略。但是，如果字符串末尾有空格，则很难检测到最后一个单词的长度。这可以通过修剪字符串之前或结尾的空格来处理。如果修改给定字符串受到限制，我们需要创建字符串的副本并从中修剪空格。

C++

// C++ program for implementation of simple
// approach to find length of last word
#include
#include 
using namespace std;
 
int lengthOfLastWord(string a)
{
    int len = 0;
     
    /* String a is 'final'-- can not be modified
    So, create a copy and trim the spaces from
    both sides */
    string str(a);
    boost::trim_right(str);
    for (int i = 0; i < str.length(); i++)
    {
        if (str.at(i) == ' ')
            len = 0;
        else
            len++;
    }
    return len;
}
 
// Driver code
int main()
{
    string input = "Geeks For Geeks ";
    cout << "The length of last word is "
        << lengthOfLastWord(input);
}
 
// This code is contributed by Rajput-Ji

Java

// Java program for implementation of simple
// approach to find length of last word
public class GFG {
    public int lengthOfLastWord(final String a)
    {
        int len = 0;
 
        /* String a is 'final'-- can not be modified
           So, create a copy and trim the spaces from
           both sides */
        String x = a.trim();
 
        for (int i = 0; i < x.length(); i++) {
            if (x.charAt(i) == ' ')
                len = 0;
            else
                len++;
        }
 
        return len;
    }
 
    // Driver code
    public static void main(String[] args)
    {
        String input = "Geeks For Geeks  ";
        GFG gfg = new GFG();
        System.out.println("The length of last word is " + gfg.lengthOfLastWord(input));
    }
}

Python3

# Python3 program for implementation of simple
# approach to find length of last word
def lengthOfLastWord(a):
    l = 0
 
    # String a is 'final'-- can not be modified
    # So, create a copy and trim the spaces from
    # both sides
    x = a.strip()
 
    for i in range(len(x)):
        if x[i] == " ":
            l = 0
        else:
            l += 1
    return l
 
# Driver code
if __name__ == "__main__":
    inp = "Geeks For Geeks "
    print("The length of last word is",
                 lengthOfLastWord(inp))
 
# This code is contributed by
# sanjeev2552

C#

// C# program for implementation of simple
// approach to find length of last word
using System;
 
class GFG {
 
    public virtual int lengthOfLastWord(string a)
    {
        int len = 0;
 
        // String a is 'final'-- can
        // not be modified So, create
        // a copy and trim the
        // spaces from both sides
        string x = a.Trim();
 
        for (int i = 0; i < x.Length; i++) {
            if (x[i] == ' ') {
                len = 0;
            }
            else {
                len++;
            }
        }
 
        return len;
    }
 
    // Driver code
    public static void Main(string[] args)
    {
        string input = "Geeks For Geeks ";
        GFG gfg = new GFG();
        Console.WriteLine("The length of last word is "
                          + gfg.lengthOfLastWord(input));
    }
}
 
// This code is contributed by shrikanth13

Javascript

 
// js program for implementation of simple
// approach to find length of last word
 
 
function lengthOfLastWord(a)
{
    let len = 0;
 
    // String a is 'final'-- can
    // not be modified So, create
    // a copy and trim the
    // spaces from both sides
    x = a.trim();
 
    for (let i = 0; i < x.length; i++) {
        if (x[i] == ' ') {
            len = 0;
        }
        else {
            len++;
        }
    }
 
    return len;
}
 
// Driver code
 
input = "Geeks For Geeks ";
document.write("The length of last word is "+ lengthOfLastWord(input));
 
 
 

输出：

Length of the last word is 5

方法2：从最后一个索引迭代字符串。这个想法更有效，因为我们可以很容易地忽略最后一个空格。这个想法是当您遇到从最后一个字母开始的第一个字母时开始增加计数，并在遇到这些字母之后的空格时停止。

C++

// CPP program for implementation of efficient
// approach to find length of last word
#include 
#include 
using namespace std;
 
int length(string str)
{
    int count = 0;
    bool flag = false;
    for (int i = str.length() - 1; i >= 0; i--) {
        // Once the first character from last
        // is encountered, set char_flag to true.
        if ((str[i] >= 'a' && str[i] <= 'z') || (str[i] >= 'A' && str[i] <= 'Z')) {
            flag = true;
            count++;
        }
        // When the first space after the
        // characters (from the last) is
        // encountered, return the length
        // of the last word
        else {
            if (flag == true)
                return count;
        }
    }
    return count;
}
 
// Driver code
int main()
{
    string str = "Geeks for Geeks";
    cout << "The length of last word is " << length(str);
    return 0;
}
 
// This code is contributed by rahulkumawat2107

Java

// Java program for implementation of efficient
// approach to find length of last word
public class GFG {
    public int lengthOfLastWord(final String a)
    {
        boolean char_flag = false;
        int len = 0;
        for (int i = a.length() - 1; i >= 0; i--) {
            if (Character.isLetter(a.charAt(i))) {
                // Once the first character from last
                // is encountered, set char_flag to true.
                char_flag = true;
                len++;
            }
            else {
                // When the first space after the characters
                // (from the last) is encountered, return the
                // length of the last word
                if (char_flag == true)
                    return len;
            }
        }
        return len;
    }
 
    // Driver code
    public static void main(String[] args)
    {
        String input = "Geeks For Geeks  ";
        GFG gfg = new GFG();
        System.out.println("The length of last word is " + gfg.lengthOfLastWord(input));
    }
}

Python3

# Python3 program for implementation of efficient
# approach to find length of last word
def length(str):
 
    count = 0;
    flag = False;
    length = len(str)-1;
    while(length != 0):
        if(str[length] == ' '):
            return count;
        else:
            count += 1;
        length -= 1;
    return count;
 
# Driver code
str = "Geeks for Geeks";
print("The length of last word is",
                      length(str));
 
# This code is contributed by Rajput Ji

C＃

// C# program for implementation of efficient
// approach to find length of last word
using System;
 
class GFG {
 
    public virtual int lengthOfLastWord(string a)
    {
        bool char_flag = false;
        int len = 0;
        for (int i = a.Length - 1; i >= 0; i--) {
            if (char.IsLetter(a[i])) {
                // Once the first character from last
                // is encountered, set char_flag to true.
                char_flag = true;
                len++;
            }
            else {
                // When the first space after the
                // characters (from the last) is
                // encountered, return the length
                // of the last word
                if (char_flag == true) {
                    return len;
                }
            }
        }
        return len;
    }
 
    // Driver code
    public static void Main(string[] args)
    {
        string input = "Geeks For Geeks ";
        GFG gfg = new GFG();
        Console.WriteLine("The length of last word is " + gfg.lengthOfLastWord(input));
    }
}
 
// This code is contributed by Shrikant13

PHP

=0 ; $i--)
    {
        // Once the first character from last
        // is encountered, set char_flag to true.
        if( ($str[$i] >='a' && $str[$i]<='z') ||
            ($str[$i] >='A' && $str[$i]<='Z'))
        {
            $flag = true;
            $count++;
        }
         
        // When the first space after the
        // characters (from the last) is
        // encountered, return the length
        // of the last word
        else
        {
            if($flag == true)
                return $count;
        }
         
    }
    return $count;
}
 
// Driver code
$str = "Geeks for Geeks";
echo "The length of last word is ", length($str);
 
// This code is contributed by ajit.
?>

输出：

Length of the last word is 5

方法#3：使用 split() 和 list

• 因为句子中的所有单词都用空格分隔。
• 我们必须使用split() 将句子按空格分隔。
• 我们用空格分割所有单词并将它们存储在一个列表中。
• 打印列表最后一个单词的长度。

下面是实现：

Python3

# Python3 program for implementation of efficient
# approach to find length of last word
 
 
def length(str):
  # Split by space and converting
    # String to list and
    lis = list(str.split(" "))
    return len(lis[-1])
 
 
# Driver code
str = "Geeks for Geeks"
print("The length of last word is",
      length(str))
 
# This code is contributed by vikkycirus

Javascript

 
// Javascript program for implementation
// of efficient approach to find length
// of last word
function length(str)
{
     
    // Split by space and converting
    // String to list and
    var lis = str.split(" ")
    return lis[lis.length - 1].length;
}
 
// Driver code
var str = "Geeks for Geeks"
document.write("The length of last word is " +
               length(str));
 
// This code is contributed by bunnyram19
 

输出：

Length of the last word is 5