LeetCode/go/edit-distance.go

package main

const UNSET int = -1

type Solver struct {
	word1 string
	word2 string
	dp    [][]int
}

func makeSolver(word1, word2 string) Solver {
	dp := make([][]int, len(word1))
	for i := range len(word1) {
		dp[i] = make([]int, len(word2))
		for j := range len(word2) {
			dp[i][j] = UNSET
		}
	}

	return Solver{
		word1: word1,
		word2: word2,
		dp:    dp,
	}
}

func (s *Solver) solve(i, j int) int {
	if i >= len(s.word1) {
		return len(s.word2) - j
	}

	if j >= len(s.word2) {
		return len(s.word1) - i
	}

	if s.dp[i][j] != UNSET {
		return s.dp[i][j]
	}

	if s.word1[i] == s.word2[j] {
		s.dp[i][j] = s.solve(i+1, j+1)
	} else {
		inserting := 1 + s.solve(i, j+1)
		deleting := 1 + s.solve(i+1, j)
		replacing := 1 + s.solve(i+1, j+1)

		s.dp[i][j] = min(inserting, min(deleting, replacing))
	}

	return s.dp[i][j]
}

func (s *Solver) Solve() int {
	return s.solve(0, 0)
}

func minDistance(word1 string, word2 string) int {
	solver := makeSolver(word1, word2)
	return solver.Solve()
}