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0072.go
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0072.go
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// Source: https://leetcode.com/problems/edit-distance
// Title: Edit Distance
// Difficulty: Hard
// Author: Mu Yang <http://muyang.pro>
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
// 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 <= 500
// word1 and word2 consist of lowercase English letters.
//
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
package main
// Apply 2D Needleman-Wunsch Algorithm
func minDistance(word1 string, word2 string) int {
m := len(word1)
n := len(word2)
mat := make([][]int, m+1)
for i := 0; i <= m; i++ {
mat[i] = make([]int, n+1)
}
for j := 0; j <= n; j++ {
mat[0][j] = j
}
// DP
for i, c1 := range word1 {
mat[i+1][0] = i + 1
for j, c2 := range word2 {
mat[i+1][j+1] = _min(mat[i][j+1], mat[i+1][j]) + 1
if c1 == c2 {
mat[i+1][j+1] = _min(mat[i+1][j+1], mat[i][j])
} else {
mat[i+1][j+1] = _min(mat[i+1][j+1], mat[i][j]+1)
}
}
}
return mat[m][n]
}
// Apply 1D Needleman-Wunsch Algorithm
func minDistance2(word1 string, word2 string) int {
n := len(word2)
prev := make([]int, n+1)
next := make([]int, n+1)
for j := 0; j <= n; j++ {
prev[j] = j
}
// DP
for i, c1 := range word1 {
next[0] = i + 1
for j, c2 := range word2 {
next[j+1] = _min(next[j], prev[j+1]) + 1
if c1 == c2 {
next[j+1] = _min(next[j+1], prev[j])
} else {
next[j+1] = _min(next[j+1], prev[j]+1)
}
}
prev, next = next, prev
}
return prev[n]
}
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
func _min(a, b int) int {
if a < b {
return a
}
return b
}