LeetCode-in-All
72. Edit Distance
Hard
Given two strings word1 and word2, return the minimum number of operations required to convert word1 to word2.
You have the following three operations permitted on a word:
- Insert a character
- Delete a character
- Replace a character
Example 1:
Input: word1 = “horse”, word2 = “ros”
Output: 3
Explanation: horse -> rorse (replace ‘h’ with ‘r’) rorse -> rose (remove ‘r’) rose -> ros (remove ‘e’)
Example 2:
Input: word1 = “intention”, word2 = “execution”
Output: 5
Explanation: intention -> inention (remove ‘t’) inention -> enention (replace ‘i’ with ‘e’) enention -> exention (replace ‘n’ with ‘x’) exention -> exection (replace ‘n’ with ‘c’) exection -> execution (insert ‘u’)
Constraints:
0 <= word1.length, word2.length <= 500word1andword2consist of lowercase English letters.
Solution
class Solution {
/**
* @param String $word1
* @param String $word2
* @return Integer
*/
public function minDistance($word1, $word2) {
$n1 = strlen($word1);
$n2 = strlen($word2);
if ($n2 > $n1) {
return $this->minDistance($word2, $word1);
}
$dp = array_fill(0, $n2 + 1, 0);
for ($j = 0; $j <= $n2; $j++) {
$dp[$j] = $j;
}
for ($i = 1; $i <= $n1; $i++) {
$pre = $dp[0];
$dp[0] = $i;
for ($j = 1; $j <= $n2; $j++) {
$tmp = $dp[$j];
$dp[$j] =
$word1[$i - 1] != $word2[$j - 1]
? 1 + min($pre, min($dp[$j], $dp[$j - 1]))
: $pre;
$pre = $tmp;
}
}
return $dp[$n2];
}
}