查找字符串最长的数字

给定字符串数字和字符。编写程序以查找字符串具有最大位数的数字。

注意：该数字可能不是字符串的最大数字。例如，如果字符串是“ a123bc321”，则答案可能是123或321，因为问题是要找到长度最长而不是最大值的数字。

例子：

Input: geeks100for1234geeks
Output: 1234

Input: abx12321bst1234yz
Output: 12321

方法：想法是遍历字符串，如果遇到数字，请存储其位置，并从该位置进一步遍历直到出现字符。每次遇到连续的数字序列时，请存储其长度，并将其长度与先前查找到的数字序列的长度相匹配，以找出所有连续的数字序列中的最大值。

下面是上述方法的实现。

C++

// C++ code for finding the longest
// length integer
#include 
using namespace std;
  
string longestInteger(string str, int l)
{
    int count = 0, max = 0, pos = -1, pre_pos, pre_len, len = 0;
    // Traverse the string
    for (int i = 0; i < l; i++) {
        // Store the previous position and previous length
        // of the digits encountered.
        pre_pos = pos;
        pre_len = len;
        count = 0;
        len = 0;
  
        // If first digit occurs, store its position in pos
        if (isdigit(str[i]))
            pos = i;
  
        // Traverse the string till a character occurs.
        while (isdigit(str[i])) {
            count++;
            i++;
            len++;
        }
  
        // Check if the length of the string is
        // greater than the previous ones or not.
        if (count > max) {
            max = count;
        }
        else {
            pos = pre_pos;
            len = pre_len;
        }
    }
    return (str.substr(pos, len));
}
  
// Driver code
int main()
{
    string str = "geeks100for1234geeks";
    int l = str.length();
    cout << longestInteger(str, l);
    return 0;
}

Java

// Java code for finding the 
// longest length integer
import java.io.*;
import java.util.*;
import java.lang.*;
  
class GFG
{
static String longestInteger(String str, int l)
{
    int count = 0, max = 0, 
        pos = -1, pre_pos, 
        pre_len, len = 0;
      
    // Traverse the string
    for (int i = 0; i < l; i++) 
    {
        // Store the previous position
        // and previous length of the
        // digits encountered.
        pre_pos = pos;
        pre_len = len;
        count = 0;
        len = 0;
  
        // If first digit occurs,
        // store its position in pos
        if (Character.isDigit(str.charAt(i)))
            pos = i;
  
        // Traverse the string 
        // till a character occurs.
        while (Character.isDigit(str.charAt(i))) 
        {
            count++;
            i++;
            len++;
        }
  
        // Check if the length of 
        // the string is greater
        // than the previous ones 
        // or not.
        if (count > max)
        {
            max = count;
        }
        else
        {
            pos = pre_pos;
            len = pre_len;
        }
    }
    return (str.substring(pos, pos + len));
}
  
// Driver code
public static void main(String[] args)
{
    String str = "geeks100for1234geeks";
    int l = str.length();
    System.out.print(longestInteger(str, l));
}
}

C#

// C# code for finding the 
// longest length integer
using System;
  
class GFG
{
static string longestInteger(string str, 
                             int l)
{
    int count = 0, max = 0, 
        pos = -1, pre_pos, 
        pre_len, len = 0;
      
    // Traverse the string
    for (int i = 0; i < l; i++) 
    {
        // Store the previous position
        // and previous length of the
        // digits encountered.
        pre_pos = pos;
        pre_len = len;
        count = 0;
        len = 0;
  
        // If first digit occurs,
        // store its position in pos
        if (Char.IsDigit(str[i]))
            pos = i;
  
        // Traverse the string 
        // till a character occurs.
        while (Char.IsDigit(str[i])) 
        {
            count++;
            i++;
            len++;
        }
  
        // Check if the length of 
        // the string is greater
        // than the previous ones 
        // or not.
        if (count > max)
        {
            max = count;
        }
        else
        {
            pos = pre_pos;
            len = pre_len;
        }
    }
    return (str.Substring(pos, len));
}
  
// Driver code
public static void Main()
{
    string str = "geeks100for1234geeks";
    int l = str.Length;
    Console.Write(longestInteger(str, l));
}
}
  
// This code is contributed 
// by ChitraNayal

Python 3

# Python 3 code for finding the 
# longest length integer
  
def longestInteger(s, length):
    count = 0
    maximum = 0
    pos = -1
    l = 0
      
    # Traverse the string
    for i in range(length):
          
        # Store the previous position
        # and previous length of 
        # the digits encountered.
        pre_pos = pos
        pre_len = l
        count = 0
        l = 0
  
        # If first digit occurs,
        # store its position in pos
        if (s[i].isdecimal()):
            pos = i
  
        # Traverse the string 
        # till a character occurs.
        while (s[i].isdecimal()):
            count += 1
            i += 1
            l += 1
  
        # Check if the length of 
        # the string is greater 
        # than the previous ones
        # or not.
        if (count > maximum):
            maximum = count
          
        else:
            pos = pre_pos
            l = pre_len
  
    return (s[pos: pos + l])
  
# Driver code
s = "geeks100for1234geeks"
length = len(s)
print(longestInteger(s, length))
  
# This code is contributed 
# by ChitraNayal

PHP

 $max)
        {
            $max = $count;
        }
        else 
        {
            $pos = $pre_pos;
            $len = $pre_len;
        }
    }
    return (substr($str, $pos, $len));
}
  
// Driver code
$str = "geeks100for1234geeks";
$l = strlen($str);
echo longestInteger($str, $l);
  
// This code is contributed
// by ChitraNayal
?>

输出：

1234

时间复杂度： O(n)
辅助空间复杂度： O(1)

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