从字符串中查找第一个最大长度偶数单词

给定字符串由空格分隔的单词。任务是从字符串中找到第一个最大长度偶数单词。例如：“给你一个包含 n 个数字的数组”答案是“an”而不是“of”，因为“an”在“of”之前。
例子：

Input:  "this is a test string"
Output:  string
Even length words are this, is, test, string. Even
maximum length word is string.

Input:  "geeksforgeeks is a platform for geeks"
Output:  platform
Only even length word is platform.

方法：想法是遍历输入字符串并找到每个单词的长度。检查单词的长度是否均匀。如果是偶数，则将长度与迄今为止找到的最大长度进行比较。如果长度严格大于最大长度，则将当前单词存储为所需的字符串。
以下是上述方法的实现：

C++

// C++ program to find maximum length even word
 
#include 
using namespace std;
 
// Function to find maximum length even word
string findMaxLenEven(string str)
{
    int n = str.length();
 
    int i = 0;
 
    // To store length of current word.
    int currlen = 0;
 
    // To store length of maximum length word.
    int maxlen = 0;
 
    // To store starting index of maximum
    // length word.
    int st = -1;
 
    while (i < n) {
 
        // If current character is space then
        // word has ended. Check if it is even
        // length word or not. If yes then
        // compare length with maximum length
        // found so far.
        if (str[i] == ' ') {
            if (currlen % 2 == 0) {
                if (maxlen < currlen) {
                    maxlen = currlen;
                    st = i - currlen;
                }
            }
 
            // Set currlen to zero for next word.
            currlen = 0;
        }
        else {
            // Update length of current word.
            currlen++;
        }
 
        i++;
    }
 
    // Check length of last word.
    if (currlen % 2 == 0) {
        if (maxlen < currlen) {
            maxlen = currlen;
            st = i - currlen;
        }
    }
 
    // If no even length word is present
    // then return -1.
    if (st == -1)
        return "-1";
 
    return str.substr(st, maxlen);
}
 
// Driver code
int main()
{
    string str = "this is a test string";
 
    cout << findMaxLenEven(str);
 
    return 0;
}

Java

// Java program to find maximum length even word
class GFG
{
     
// Function to find maximum length even word
static String findMaxLenEven(String str)
{
    int n = str.length();
 
    int i = 0;
 
    // To store length of current word.
    int currlen = 0;
 
    // To store length of maximum length word.
    int maxlen = 0;
 
    // To store starting index of maximum
    // length word.
    int st = -1;
 
    while (i < n)
    {
 
        // If current character is space then
        // word has ended. Check if it is even
        // length word or not. If yes then
        // compare length with maximum length
        // found so far.
        if (str.charAt(i) == ' ')
        {
            if (currlen % 2 == 0)
            {
                if (maxlen < currlen)
                {
                    maxlen = currlen;
                    st = i - currlen;
                }
            }
 
            // Set currlen to zero for next word.
            currlen = 0;
        }
        else
        {
            // Update length of current word.
            currlen++;
        }
 
        i++;
    }
 
    // Check length of last word.
    if (currlen % 2 == 0)
    {
        if (maxlen < currlen)
        {
            maxlen = currlen;
            st = i - currlen;
        }
    }
 
    // If no even length word is present
    // then return -1.
    if (st == -1)
        return "-1";
 
    return str.substring(st, st + maxlen);
}
 
// Driver code
public static void main(String args[])
{
    String str = "this is a test string";
 
    System.out.println( findMaxLenEven(str));
}
}
 
// This code is contributed by Arnab Kundu

Python 3

# Python3 program to find maximum
# length even word
 
# Function to find maximum length
# even word
def findMaxLenEven(str):
    n = len(str)
    i = 0
 
    # To store length of current word.
    currlen = 0
 
    # To store length of maximum length word.
    maxlen = 0
 
    # To store starting index of maximum
    # length word.
    st = -1
 
    while (i < n):
 
        # If current character is space then
        # word has ended. Check if it is even
        # length word or not. If yes then
        # compare length with maximum length
        # found so far.
        if (str[i] == ' '):
            if (currlen % 2 == 0):
                if (maxlen < currlen):
                    maxlen = currlen
                    st = i - currlen
 
            # Set currlen to zero for next word.
            currlen = 0
         
        else :
             
            # Update length of current word.
            currlen += 1
 
        i += 1
 
    # Check length of last word.
    if (currlen % 2 == 0):
        if (maxlen < currlen):
            maxlen = currlen
            st = i - currlen
 
    # If no even length word is present
    # then return -1.
    if (st == -1):
        print("trie")
        return "-1"
     
    return str[st: st + maxlen]
 
# Driver code
if __name__ == "__main__":
     
    str = "this is a test string"
 
    print(findMaxLenEven(str))
 
# This code is contributed by Ita_c

C#

// C# program to find maximum length even word
 
using System;
 
class GFG
{
     
    // Function to find maximum length even word
    static String findMaxLenEven(string str)
    {
        int n = str.Length;
     
        int i = 0;
     
        // To store length of current word.
        int currlen = 0;
     
        // To store length of maximum length word.
        int maxlen = 0;
     
        // To store starting index of maximum
        // length word.
        int st = -1;
     
        while (i < n)
        {
     
            // If current character is space then
            // word has ended. Check if it is even
            // length word or not. If yes then
            // compare length with maximum length
            // found so far.
            if (str[i] == ' ')
            {
                if (currlen % 2 == 0)
                {
                    if (maxlen < currlen)
                    {
                        maxlen = currlen;
                        st = i - currlen;
                    }
                }
     
                // Set currlen to zero for next word.
                currlen = 0;
            }
            else
            {
                // Update length of current word.
                currlen++;
            }
     
            i++;
        }
     
        // Check length of last word.
        if (currlen % 2 == 0)
        {
            if (maxlen < currlen)
            {
                maxlen = currlen;
                st = i - currlen;
            }
        }
     
        // If no even length word is present
        // then return -1.
        if (st == -1)
            return "-1";
     
        return str.Substring(st, maxlen);
    }
 
    // Driver code
    public static void Main()
    {
        string str = "this is a test string";
     
        Console.WriteLine(findMaxLenEven(str));
    }
    // This code is contributed by Ryuga
}

Javascript

 
 
// Javascript program to find maximum length even word
 
// Function to find maximum length even word
function findMaxLenEven(str)
{
    var n = str.length;
 
    var i = 0;
 
    // To store length of current word.
    var currlen = 0;
 
    // To store length of maximum length word.
    var maxlen = 0;
 
    // To store starting index of maximum
    // length word.
    var st = -1;
 
    while (i < n) {
 
        // If current character is space then
        // word has ended. Check if it is even
        // length word or not. If yes then
        // compare length with maximum length
        // found so far.
        if (str[i] == ' ') {
            if (currlen % 2 == 0) {
                if (maxlen < currlen) {
                    maxlen = currlen;
                    st = i - currlen;
                }
            }
 
            // Set currlen to zero for next word.
            currlen = 0;
        }
        else {
            // Update length of current word.
            currlen++;
        }
 
        i++;
    }
 
    // Check length of last word.
    if (currlen % 2 == 0) {
        if (maxlen < currlen) {
            maxlen = currlen;
            st = i - currlen;
        }
    }
 
    // If no even length word is present
    // then return -1.
    if (st == -1)
        return "-1";
 
    return str.substr(st, maxlen);
}
 
// Driver code
var str = "this is a test string";
document.write( findMaxLenEven(str));
 
// This code is contributed by noob2000.

输出：

string

时间复杂度： O(N)，其中 N 是字符串的长度。
辅助空间： O(1)