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1
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<?php |
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2
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3
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declare(strict_types=1); |
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4
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5
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namespace leetcode; |
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6
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7
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class BackspaceStringCompare |
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8
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{ |
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9
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public static function backspaceCompare(string $s, string $t): bool |
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10
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{ |
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11
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if (empty($s) || empty($t)) { |
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12
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return false; |
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} |
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14
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$helper = static function (string &$s, int &$i) { |
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$n = 0; |
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while ($i >= 0 && ($n > 0 || $s[$i] === '#')) { |
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$n = $s[$i] === '#' ? $n + 1 : $n - 1; |
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$i--; |
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} |
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return $i >= 0 ? $s[$i] : '#'; |
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}; |
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[$i, $j] = [strlen($s) - 1, strlen($t) - 1]; |
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while ($i >= 0 || $j >= 0) { |
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$p = $helper($s, $i); |
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$q = $helper($t, $j); |
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if ($p !== $q) { |
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return false; |
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} |
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$i--; |
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$j--; |
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} |
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32
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33
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return true; |
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} |
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36
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public static function backspaceCompare2(string $s, string $t): bool |
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{ |
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if (empty($s) || empty($t)) { |
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return false; |
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40
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} |
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41
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[$i, $j] = [strlen($s) - 1, strlen($t) - 1]; |
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$m = $n = 0; |
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while (true) { |
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while ($i >= 0 && ($m > 0 || $s[$i] === '#')) { |
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$m += $s[$i] === '#' ? 1 : -1; |
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$i--; |
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} |
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48
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while ($j >= 0 && ($n > 0 || $t[$j] === '#')) { |
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$n += $t[$j] === '#' ? 1 : -1; |
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$j--; |
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51
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} |
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52
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if ($i >= 0 && $j >= 0 && $s[$i] === $t[$j]) { |
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$i--; |
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$j--; |
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} else { |
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break; |
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57
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} |
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58
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} |
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59
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60
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return $i === -1 && $j === -1; |
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61
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} |
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63
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public static function backspaceCompare3(string $s, string $t): bool |
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64
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{ |
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65
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if (empty($s) || empty($t)) { |
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66
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return false; |
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67
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} |
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68
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$helper = static function (string $s, array $stack) { |
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69
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$n = strlen($s); |
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70
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for ($i = 0; $i < $n; $i++) { |
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if ($s[$i] === '#') { |
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if (!$stack) { |
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continue; |
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74
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} |
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75
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array_pop($stack); |
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} else { |
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array_push($stack, $s[$i]); |
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} |
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} |
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return $stack; |
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81
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}; |
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82
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[$p, $q] = [$helper($s, []), $helper($t, [])]; |
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83
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84
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return $p === $q; |
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85
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} |
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86
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} |
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87
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imajinyun /
leetcode-php
This check marks implicit conversions of arrays to boolean values in a comparison. While in PHP an empty array is considered to be equal (but not identical) to false, this is not always apparent.
Consider making the comparison explicit by using
empty(..)or! empty(...)instead.