查找两个字符串的不常见字符

按排序顺序查找并打印两个给定字符串的不常见字符。这里不常见的字符意味着该字符要么出现在一个字符串，要么出现在另一个字符串但不同时出现在这两个字符串中。字符串仅包含小写字符并且可以包含重复项。
资料来源：亚马逊面试体验 | 355套（1年经验）
例子：

Input: str1 = “characters”, str2 = “alphabets” 
Output: b c l p r
Input: str1 = “geeksforgeeks”, str2 = “geeksquiz” 
Output: f i o q r u z

朴素的方法：使用两个循环，对于第一个字符串的每个字符检查它是否存在于第二个字符串。同样，对于第二个字符串的每个字符，检查它是否存在于第一个字符串。
时间复杂度：需要 O(n^2) 和额外的来处理重复项。
有效的方法：一种有效的方法是使用散列。

• 对所有小写字符使用大小为 26 的哈希表。
• 最初，将每个字符的存在标记为“0”（表示该字符不存在于两个字符串）。
• 遍历第一个字符串，并将哈希表中第一个字符串的每个字符的存在标记为“1”（表示第一个字符串）。
• 现在，遍历第二个字符串。对于 2nd 字符串 的每个字符，检查它在哈希表中的存在是否为“1”。如果它是“1”，则将其存在标记为“-1”（表示该字符对两个字符串是共同的），否则将其存在标记为“2”（表示第二个字符串）。

下图是上述方法的试运行：

下面是上述方法的实现：

C++

// C++ implementation to find the uncommon
// characters of the two strings
#include 
using namespace std;
 
// size of the hash table
const int MAX_CHAR = 26;
 
// function to find the uncommon characters
// of the two strings
void findAndPrintUncommonChars(string str1, string str2)
{
    // mark presence of each character as 0
    // in the hash table 'present[]'
    int present[MAX_CHAR];
    for (int i=0; i

---

Java

// Java implementation to find the uncommon
// characters of the two strings
class GFG
{
 
    // size of the hash table
    static int MAX_CHAR = 26;
 
    // function to find the uncommon
    // characters of the two strings
    static void findAndPrintUncommonChars(String str1,
                                       String str2)
    {
        // mark presence of each character as 0
        // in the hash table 'present[]'
        int present[] = new int[MAX_CHAR];
        for (int i = 0; i < MAX_CHAR; i++)
        {
            present[i] = 0;
        }
 
        int l1 = str1.length();
        int l2 = str2.length();
 
        // for each character of str1, mark its
        // presence as 1 in 'present[]'
        for (int i = 0; i < l1; i++)
        {
            present[str1.charAt(i) - 'a'] = 1;
        }
 
        // for each character of str2
        for (int i = 0; i < l2; i++)
        {
             
            // if a character of str2 is also present
            // in str1, then mark its presence as -1
            if (present[str2.charAt(i) - 'a'] == 1
                || present[str2.charAt(i) - 'a'] == -1)
            {
                present[str2.charAt(i) - 'a'] = -1;
            }
             
            // else mark its presence as 2
            else
            {
                present[str2.charAt(i) - 'a'] = 2;
            }
        }
 
        // print all the uncommon characters
        for (int i = 0; i < MAX_CHAR; i++)
        {
            if (present[i] == 1 || present[i] == 2)
            {
                System.out.print((char) (i + 'a') + " ");
            }
        }
    }
 
    // Driver code
    public static void main(String[] args)
    {
        String str1 = "characters";
        String str2 = "alphabets";
        findAndPrintUncommonChars(str1, str2);
    }
}
 
// This code is contributed by Rajput-JI

Python 3

# Python 3 implementation to find the
# uncommon characters of the two strings
 
# size of the hash table
MAX_CHAR = 26
 
# function to find the uncommon characters
# of the two strings
def findAndPrintUncommonChars(str1, str2):
     
    # mark presence of each character as 0
    # in the hash table 'present[]'
    present = [0] * MAX_CHAR
    for i in range(0, MAX_CHAR):
        present[i] = 0
 
    l1 = len(str1)
    l2 = len(str2)
     
    # for each character of str1, mark its
    # presence as 1 in 'present[]'
    for i in range(0, l1):
        present[ord(str1[i]) - ord('a')] = 1
         
    # for each character of str2
    for i in range(0, l2):
         
        # if a character of str2 is also present
        # in str1, then mark its presence as -1
        if(present[ord(str2[i]) - ord('a')] == 1 or
           present[ord(str2[i]) - ord('a')] == -1):
            present[ord(str2[i]) - ord('a')] = -1
 
        # else mark its presence as 2
        else:
            present[ord(str2[i]) - ord('a')] = 2
 
    # print all the uncommon characters
    for i in range(0, MAX_CHAR):
        if(present[i] == 1 or present[i] == 2):
            print(chr(i + ord('a')), end = " ")
 
# Driver Code
if __name__ == "__main__":
    str1 = "characters"
    str2 = "alphabets"
    findAndPrintUncommonChars(str1, str2)
 
# This code is contributed
# by Sairahul099

C#

// C# implementation to find the uncommon
// characters of the two strings
using System;
 
class GFG
{
 
    // size of the hash table
    static int MAX_CHAR = 26;
 
    // function to find the uncommon
    // characters of the two strings
    static void findAndPrintUncommonChars(String str1,
                                    String str2)
    {
        // mark presence of each character as 0
        // in the hash table 'present[]'
        int []present = new int[MAX_CHAR];
        for (int i = 0; i < MAX_CHAR; i++)
        {
            present[i] = 0;
        }
 
        int l1 = str1.Length;
        int l2 = str2.Length;
 
        // for each character of str1, mark its
        // presence as 1 in 'present[]'
        for (int i = 0; i < l1; i++)
        {
            present[str1[i] - 'a'] = 1;
        }
 
        // for each character of str2
        for (int i = 0; i < l2; i++)
        {
             
            // if a character of str2 is also present
            // in str1, then mark its presence as -1
            if (present[str2[i] - 'a'] == 1
                || present[str2[i] - 'a'] == -1)
            {
                present[str2[i] - 'a'] = -1;
            }
             
            // else mark its presence as 2
            else
            {
                present[str2[i] - 'a'] = 2;
            }
        }
 
        // print all the uncommon characters
        for (int i = 0; i < MAX_CHAR; i++)
        {
            if (present[i] == 1 || present[i] == 2)
            {
                Console.Write((char) (i + 'a') + " ");
            }
        }
    }
 
    // Driver code
    public static void Main(String[] args)
    {
        String str1 = "characters";
        String str2 = "alphabets";
        findAndPrintUncommonChars(str1, str2);
    }
}
 
// This code is contributed by PrinciRaj1992

Javascript

// Javascript implementation to find the uncommon
// characters of the two strings
 
// size of the hash table
var MAX_CHAR = 26;
 
// function to find the uncommon characters
// of the two strings
function findAndPrintUncommonChars(str1, str2)
{
    // mark presence of each character as 0
    // in the hash table 'present[]'
    var present = Array(MAX_CHAR);
    for (var i = 0; i < MAX_CHAR; i++)
        present[i] = 0;
 
    var l1 = str1.length;
    var l2 = str2.length;
 
    // for each character of str1, mark its
    // presence as 1 in 'present[]'
    for (var i = 0; i < l1; i++)
        present[str1[i].charCodeAt(0) - 'a'.charCodeAt(0)] = 1;
 
    // for each character of str2
    for (var i = 0; i < l2; i++)
    {
        // if a character of str2 is also present
        // in str1, then mark its presence as -1
        if (present[str2[i].charCodeAt(0) - 'a'.charCodeAt(0)] == 1
            || present[str2[i].charCodeAt(0) - 'a'.charCodeAt(0)] == -1)
            present[str2[i].charCodeAt(0) - 'a'.charCodeAt(0)] = -1;
 
        // else mark its presence as 2
        else
            present[str2[i].charCodeAt(0) - 'a'.charCodeAt(0)] = 2;
    }
 
    // print all the uncommon characters
    for (var i=0; i<MAX_CHAR; i++)
        if (present[i] == 1 || present[i] == 2 )
            document.write( (String.fromCharCode(i + 'a'.charCodeAt(0))) + " ");
}
 
// Driver program to test above
var str1 = "characters";
var str2 = "alphabets";
findAndPrintUncommonChars(str1, str2);
 
// This code is contributed by importantly.

输出：

b c l p r

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