给定数字 N 中唯一数字的计数

给定一个数字N ，任务是计算给定数字中唯一数字的数量。

例子：

Input: N = 22342 
Output: 2 
Explanation:
The digits 3 and 4 occurs only once. Hence, the output is 2.

Input: N = 99677 
Output: 1
Explanation:
The digit 6 occurs only once. Hence, the output is 1. 

朴素的方法：通过这种方法，可以使用两个嵌套循环来解决问题。在第一个循环中，从数字的第一个数字到最后一个数字，一个一个地遍历。然后对于第一个循环中的每个数字，运行第二个循环并搜索该数字是否存在于数字中的其他任何地方。如果否，则将所需计数加 1。最后，打印计算出的所需计数。
时间复杂度： O(L ² )
辅助空间： O(1)

高效的方法：想法是使用哈希来存储数字的频率，然后对频率等于1的数字进行计数。请按照以下步骤解决问题：

1. 为数字 0-9 创建一个大小为 10 的哈希表。最初将每个索引存储为 0。
2. 现在，对于数字 N 的每一位，增加哈希表中该索引的计数。
3. 遍历哈希表并计算值等于 1 的索引。
4. 最后，打印/返回这个计数。

下面是上述方法的实现：

C++

// C++ program for the above approach
#include 
using namespace std;
 
// Function that returns the count of
// unique digits of the given number
int countUniqueDigits(int N)
{
    // Initialize a variable to store
    // count of unique digits
    int res = 0;
 
    // Initialize cnt array to store
    // digit count
    int cnt[10] = { 0 };
 
    // Iterate through the digits of N
    while (N > 0) {
 
        // Retrieve the last digit of N
        int rem = N % 10;
 
        // Increase the count
        // of the last digit
        cnt[rem]++;
 
        // Remove the last digit of N
        N = N / 10;
    }
 
    // Iterate through the cnt array
    for (int i = 0; i < 10; i++) {
 
        // If frequency of
        // digit is 1
        if (cnt[i] == 1) {
 
            // Increment the count
            // of unique digits
            res++;
        }
    }
 
    // Return the count/ of unique digit
    return res;
}
 
// Driver Code
int main()
{
    // Given array arr[]
    int N = 2234262;
 
    // Function Call
    cout << countUniqueDigits(N);
    return 0;
}

Java

// Java program for the above approach
import java.util.*;
 
class GFG {
 
    // Function that returns the count
    // of unique digits of number N
    public static void
    countUniqueDigits(int N)
    {
        // Initialize a variable to
        // store count of unique digits
        int res = 0;
 
        // Initialize cnt array to
        // store digit count
        int cnt[] = { 0, 0, 0, 0, 0,
                      0, 0, 0, 0, 0 };
 
        // Iterate through digits of N
        while (N > 0) {
 
            // Retrieve the last
            // digit of N
            int rem = N % 10;
 
            // Increase the count
            // of the last digit
            cnt[rem]++;
 
            // Remove the last
            // digit of N
            N = N / 10;
        }
 
        // Iterate through the
        // cnt array
        for (int i = 0;
             i < cnt.length; i++) {
 
            // If frequency of
            // digit is 1
            if (cnt[i] == 1) {
 
                // Increment the count
                // of unique digits
                res++;
            }
        }
 
        // Return the count of unique digit
        System.out.println(res);
    }
 
    // Driver Code
    public static void main(String[] args)
    {
        // Given Number N
        int N = 2234262;
 
        // Function Call
        countUniqueDigits(N);
    }
}

Python3

# Python3 program for the above approach
 
# Function that returns the count of
# unique digits of the given number
def countUniqueDigits(N):
 
    # Initialize a variable to store
    # count of unique digits
    res = 0
 
    # Initialize cnt list to store
    # digit count
    cnt = [0] * 10
 
    # Iterate through the digits of N
    while (N > 0):
 
        # Retrieve the last digit of N
        rem = N % 10
 
        # Increase the count
        # of the last digit
        cnt[rem] += 1
 
        # Remove the last digit of N
        N = N // 10
 
    # Iterate through the cnt list
    for i in range(10):
 
        # If frequency of
        # digit is 1
        if (cnt[i] == 1):
 
            # Increment the count
            # of unique digits
            res += 1
 
    # Return the count of unique digit
    return res
 
# Driver Code
 
# Given number N
N = 2234262
 
# Function call
print(countUniqueDigits(N))
 
# This code is contributed by vishu2908

C#

// C# program for the above approach
using System;
 
class GFG{
 
// Function that returns the count
// of unique digits of number N
public static void countUniqueDigits(int N)
{
     
    // Initialize a variable to
    // store count of unique digits
    int res = 0;
 
    // Initialize cnt array to
    // store digit count
    int[] cnt = { 0, 0, 0, 0, 0,
                  0, 0, 0, 0, 0 };
 
    // Iterate through digits of N
    while (N > 0)
    {
         
        // Retrieve the last
        // digit of N
        int rem = N % 10;
 
        // Increase the count
        // of the last digit
        cnt[rem]++;
 
        // Remove the last
        // digit of N
        N = N / 10;
    }
 
    // Iterate through the
    // cnt array
    for(int i = 0; i < cnt.Length; i++)
    {
         
        // If frequency of
        // digit is 1
        if (cnt[i] == 1)
        {
             
            // Increment the count
            // of unique digits
            res++;
        }
    }
     
    // Return the count of unique digit
    Console.WriteLine(res);
}
 
// Driver Code
public static void Main(String[] args)
{
     
    // Given Number N
    int N = 2234262;
 
    // Function Call
    countUniqueDigits(N);
}
}
 
// This code is contributed by jrishabh99

Javascript

 
// Javascript program for the above approach
 
// Function that returns the count of
// unique digits of the given number
function countUniqueDigits(N)
{
    // Initialize a variable to store
    // count of unique digits
    let res = 0;
 
    // Initialize cnt array to store
    // digit count
    let cnt = [0, 0, 0, 0, 0,
                      0, 0, 0, 0, 0];
 
    // Iterate through the digits of N
    while (N > 0) {
 
        // Retrieve the last digit of N
        let rem = N % 10;
 
        // Increase the count
        // of the last digit
        cnt[rem]++;
 
        // Remove the last digit of N
        N = Math.floor(N / 10);
    }
 
    // Iterate through the cnt array
    for (let i = 0; i < 10; i++) {
 
        // If frequency of
        // digit is 1
        if (cnt[i] == 1) {
 
            // Increment the count
            // of unique digits
            res++;
        }
    }
 
    // Return the count/ of unique digit
    return res;
}
 
// Driver Code
 
    // Given array arr[]
    let N = 2234262;
 
    // Function Call
    document.write(countUniqueDigits(N));
     
// This code is contributed by Mayank Tyagi
 

输出：

3

时间复杂度： O(N) ，其中N是数字的位数。
辅助空间： O(1)

注意：由于使用的哈希表的大小只有 10，因此其时间和空间复杂度将接近恒定。因此不计入上述时间和辅助空间。