在数组中查找非重复元素

问题描述

我的数组是:

$array= array(4,3,4,3,1,2,1);

我想将其输出如下:

Output = 2

(因为2仅出现一次)

这是我尝试过的:

$array = array(4, 3, 4, 3, 1, 2, 1);
$array1 = array(4, 3, 4, 3, 1, 2, 1);
$array_diff = array_diff($array, $array1);

解决方案

无循环单线:(演示)

var_export(array_keys(array_intersect(array_count_values($array),[1])));

明细:

array_keys(                          // return the remaining keys from array_count_values
    array_intersect(                 // filter the first array by second
        array_count_values($array),  // count number of occurrences of each value
        [1]                          // identify the number of occurrences to keep
    )
)

如果您(或以后的读者)希望保留更多值，请替换array_intersect()中的第二个参数/数组.例如:您想保留1,2和3:array(1,2,3)或[1,2,3]

p.s.作为记录，您可以将array_filter()与自定义函数一起使用，以忽略所有非1的计数值，但是我使用了array_intersect()，因为语法更简短并且IMO更易于阅读.

---

p.s.以为我会重新考虑并加入PHP7.4技术，并与其他基于函数的技术进行比较...

代码:(演示)

$numbers = [4, 3, 4, 3, 1, 2, 1];
var_export(
    array_keys(
        array_intersect(
            array_count_values($numbers),
            [1]
        )
    )
);

echo "\n---\n";
var_export(
    array_keys(
        array_filter(
            array_count_values($numbers),
            function($count) {
                return $count === 1;
            }
        )
    )
);

echo "\n---\n";
// PHP7.4+
var_export(
    array_keys(
        array_filter(
            array_count_values($numbers),
            fn($count) => $count === 1
        )
    )
);

My array is :

$array= array(4,3,4,3,1,2,1);

And I'd like to output it like below:

Output = 2

(As 2 is present only once)

This is what I've tried:

$array = array(4, 3, 4, 3, 1, 2, 1);
$array1 = array(4, 3, 4, 3, 1, 2, 1);
$array_diff = array_diff($array, $array1);

解决方案

One-liner with no loops: (Demo)

var_export(array_keys(array_intersect(array_count_values($array),[1])));

The breakdown:

array_keys(                          // return the remaining keys from array_count_values
    array_intersect(                 // filter the first array by second
        array_count_values($array),  // count number of occurrences of each value
        [1]                          // identify the number of occurrences to keep
    )
)

if you (or any future reader) wants to keep more values, replace the second parameter/array in array_intersect().for instance:you want to keep 1,2,and 3: array(1,2,3) or [1,2,3]

p.s. For the record, you can use array_filter() with a custom function to omit all non-1 count values, but I have used array_intersect() because the syntax is more brief and IMO easier to read.

---

p.s. thought I'd revisit and include a PHP7.4 technique and compare against other function-based techniques...

Code: (Demo)

$numbers = [4, 3, 4, 3, 1, 2, 1];
var_export(
    array_keys(
        array_intersect(
            array_count_values($numbers),
            [1]
        )
    )
);

echo "\n---\n";
var_export(
    array_keys(
        array_filter(
            array_count_values($numbers),
            function($count) {
                return $count === 1;
            }
        )
    )
);

echo "\n---\n";
// PHP7.4+
var_export(
    array_keys(
        array_filter(
            array_count_values($numbers),
            fn($count) => $count === 1
        )
    )
);

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