How to deal with data deduplication in C++ development

How to deal with data deduplication in C development

In the daily C development process, we often encounter situations where we need to deal with data deduplication. Whether you are deduplicating data in one container or between multiple containers, you need to find an efficient and reliable method. This article will introduce some common data deduplication techniques to help readers deal with data deduplication problems in C development.

1. Sorting deduplication method
The sorting deduplication method is a common and simple data deduplication method. First, the data to be deduplicated is stored in a container, and then the container is sorted. After sorting, by comparing the values ​​of adjacent elements, if the adjacent elements are found to be the same, the duplicate elements are deleted to achieve the purpose of deduplication.

Code example:

#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main()
{
    vector<int> data = { 1, 2, 3, 4, 4, 5, 5, 6, 7, 8, 8 };
    
    sort(data.begin(), data.end());
    data.erase(unique(data.begin(), data.end()), data.end());
    
    for (int num : data)
        cout << num << " ";
    cout << endl;
    
    return 0;
}

The above code will output: 1 2 3 4 5 6 7 8

2. Hash table deduplication method
Hash table deduplication The duplication method is a deduplication method that trades space for time. By using a hash table, the value of each element is used as a key and the number of occurrences is used as a value, and the data to be deduplicated is added to the hash table in sequence. If an element already exists in the hash table, increase the number of occurrences of the element by one. Finally, traverse the hash table and store elements with one occurrence in a new container to complete deduplication.

Code example:

#include <iostream>
#include <vector>
#include <unordered_map>

using namespace std;

int main()
{
    vector<int> data = { 1, 2, 3, 4, 4, 5, 5, 6, 7, 8, 8 };
    
    unordered_map<int, int> hashTable;
    for (int num : data)
        hashTable[num]++;
        
    vector<int> result;
    for (auto item : hashTable)
    {
        if (item.second == 1)
            result.push_back(item.first);
    }
    
    for (int num : result)
        cout << num << " ";
    cout << endl;
    
    return 0;
}

The above code will output: 1 2 3 6 7

3. STL algorithm deduplication method
In addition to the above method, the C standard library The algorithm also provides functions for removing duplicates, such as unique and remove_if. The unique function will remove adjacent duplicate elements, while the remove_if function will determine whether to remove elements based on user-defined conditions. These two functions can be used in combination to easily deduplicate data.

Code example:

#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

bool isOdd(int num)
{
    return num % 2 != 0;
}

int main()
{
    vector<int> data = { 1, 2, 3, 4, 4, 5, 5, 6, 7, 8, 8 };
    
    auto endIter = unique(data.begin(), data.end());
    data.erase(endIter, data.end());
    
    data.erase(remove_if(data.begin(), data.end(), isOdd), data.end());
    
    for (int num : data)
        cout << num << " ";
    cout << endl;
    
    return 0;
}

The above code will output: 2 4 6 8 8

The above introduces several common methods to deal with data deduplication problems in C development. Each method has its own characteristics and applicable scenarios. In actual development, readers can choose the appropriate method according to specific needs. At the same time, readers can also implement more efficient deduplication algorithms on their own based on their data deduplication requirements and performance needs. I hope this article will help readers solve the problem of data deduplication in C development.

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