#4 LeetCode ( Q:(72) Edit Distance)

LeetCode Edit Distance, Coding Interview Question
Level : Hard
Challenge : 4

Given two words word1 and word2, find the minimum number of operations required to convert word1 to word2.

You have the following 3 operations permitted on a word:

1. Insert a character
2. Delete a character
3. 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')

Solution — Java

class Solution {
public int minDistance(String word1, String word2) {
int m = word1.length();
int n = word2.length();
int[] dp = new int[n + 1];
for (int i = 1; i <= n; i++) dp[i] = i;

for (int i = 1; i <= m; i++) {
int prev = dp[0];
dp[0] = i;
for (int j = 1; j <= n; j++) {
int tmp = dp[j];
if (word1.charAt(i — 1) != word2.charAt(j — 1)) {
dp[j] = 1 + Math.min(prev, Math.min(dp[j], dp[j — 1]));
} else {
dp[j] = prev;
}
prev = tmp;
}
}
return dp[n];
}
}