how to split a string into n parts(non-empty substring) with all possible ratios | PHP | Javascript

Let suppose, I have a string(programming language can be either PHP or js)

$s = "abcd";

I want to split this string into substrings(non-empty) into 3 parts with all possible combinations. So the output should be

$result = [
    ["a", "b", "cd"],
    ["ab", "c", "d"],
    ["a", "bc", "d"]
]

I tried with for loop, but the value is overlapped and I don't want to repeat the string.

<?php 
function solution($s) {
    $n = strlen($s);
    $result = [];
    for ($i = 0; $i < $n; $i++) {
        for ($j = $i + 1; $j < $n; $j++) {
            $s1 = substr($s, 0, $j);
            $s2 = substr($s, $i, $j);
            $s3 = substr($s, $j, $n);
            $temp = [$s1, $s2, $s3];
            array_push($result, $temp);
        }
    }
    return $result;
}

$s = "abcd";

print_r(solution($s));

?>

If I get the idea about how we can calculate the possible ratio for a single number then I have a solution ready that gives me the desired output.

<?php
$possibleRatios = [
    [1, 1, 2],
    [2, 1, 1],
    [1, 2, 1]
];

$result = [];
for ($i = 0; $i < count($possibleRatios); $i++) {
    $element = $possibleRatios[$i];
    $s1 = substr($s, 0, $element[0]);
    $s2 = substr($s, $element[0], $element[1]);
    $s3 = substr($s, $element[0] + $element[1], $element[2]);
    $temp = [$s1, $s2, $s3];
    array_push($result, $temp);
}
print_r($result);

In my case, the length of the string is 4 so I want the possible ratio 1:1:2, 2:1:1, 1:2:1. I know the other possible ratios can be 0:1:3, 1:0:3 but I actually want to skip the empty substring combination.

Solution 1:

Example in js

const string = "abcd";

const array = string.split("");

const output = array.reduce((carry, _, idx, arr) => {
    if (idx < arr.length - 1) {
        const str = arr[idx] + arr[idx + 1];
        const subArray = [...arr];
        subArray.splice(idx, 2, str);
        carry.push(subArray);
    }
    return carry;
}, []);

console.log(output);

Example in php

<?php

$str = "abcd";

$array = str_split($str);

$output = array_reduce($array, function ($carry) use ($array) {
    $idx = $carry['idx'];
    if ($idx < count($array) - 1) {
        $str = $array[$idx] . $array[$idx + 1];
        $subArray = $array;
        array_splice($subArray, $idx, 2, $str);
        $carry['output'][] = $subArray;
    }
    $carry['idx'] += 1;
    return $carry;
}, ['output' => [], 'idx' => 0])['output'];

var_dump($output);