PHP implements array deduplication algorithm

With the continuous increase of data processing, data deduplication has become a common problem in many applications. In PHP, we can use various algorithms to implement array deduplication, such as array deduplication sorting method, hash key value method, in_array method, etc. Below we introduce in detail the method of implementing array deduplication algorithm in PHP.

1. Array deduplication and sorting method

The array deduplication and sorting method is a relatively common deduplication method. Its idea is to sort the array first, and then scan the adjacent arrays. elements, compare adjacent elements, and if two adjacent elements are equal, delete one of the elements. The following is a sample code that uses the array deduplication sorting method to implement array deduplication:

function array_unique_sort($array) {
    sort($array); // 将数组按照元素值排序
    $last = null; // 记录上一个元素值
    foreach ($array as $key => $value) {
        if ($value === $last) {
            unset($array[$key]); // 删除相邻的重复元素
            continue;
        }
        $last = $value;
    }
    return $array;
}

In the above code, we first use the sort() function to sort the array. Then, we use a foreach loop to iterate through each element in the array and use a variable $last to record the value of the previous element. When two adjacent elements have equal values, we use the unset() function to delete one of the elements. Finally, the deduplicated array is returned.

2. Hash key value method

The hash key value method is another common array deduplication method. Its idea is to use a temporary array to save the elements in the array. Then use the value of the element as a hash key to save each element in the array under the corresponding hash key. If the same element value occurs, only one is saved, and finally a temporary array is returned. The following is a sample code that uses the hash key value method to implement array deduplication:

function array_unique_hash($array) {
    $temp = array(); // 临时数组
    foreach ($array as $value) {
        if (isset($temp[$value])) {
            continue; // 已经出现过的元素，跳过
        }
        $temp[$value] = $value; // 新元素，添加到临时数组中
    }
    return array_values($temp); // 返回去重后的数组
}

In the above code, we use a temporary array $temp to save the deduplicated elements. Traverse each element in the original array. If the element has already appeared, skip it; otherwise, add the element to the temporary array as key and value. Finally, we return the deduplicated results through the array_values() function.

3. in_array method

The in_array method is a relatively simple but inefficient array deduplication method. Its idea is to use the in_array() function to traverse each element in the array. Determine whether the element has already appeared in the temporary array. If not, add the element to the temporary array. The following is a sample code that uses the in_array method to implement array deduplication:

function array_unique_in_array($array) {
    $temp = array(); // 临时数组
    foreach ($array as $value) {
        if (in_array($value, $temp)) {
            continue; // 已经出现过的元素，跳过
        }
        $temp[] = $value; // 新元素，添加到临时数组中
    }
    return $temp; // 返回去重后的数组
}

In the above code, we use the in_array() function to determine whether the element has already appeared in the temporary array. If the element does not exist, it is added to the temporary array. Finally, we return the deduplicated results.

To sum up, there are many methods in PHP to implement the algorithm of array deduplication. Depending on the specific implementation requirements, we can choose the array deduplication sorting method, hash key value method and in_array method. and other methods to achieve the purpose of array deduplication.

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