The task is:
A non-empty zero-indexed string S is given. String S consists of N characters from the set of upper-case English letters A, C, G, T.
<
simple php 100/100 solution
function solution($S, $P, $Q) {
$result = array();
for ($i = 0; $i < count($P); $i++) {
$from = $P[$i];
$to = $Q[$i];
$length = $from >= $to ? $from - $to + 1 : $to - $from + 1;
$new = substr($S, $from, $length);
if (strpos($new, 'A') !== false) {
$result[$i] = 1;
} else {
if (strpos($new, 'C') !== false) {
$result[$i] = 2;
} else {
if (strpos($new, 'G') !== false) {
$result[$i] = 3;
} else {
$result[$i] = 4;
}
}
}
}
return $result;
}