072 Edit Distance

class Solution:
    # @param {string} word1
    # @param {string} word2
    # @return {integer}
    def minDistance(self, word1, word2):
        m, n = len(word1), len(word2)
        if m*n == 0:
            return max(m,n)
        dp = [[0] * (n + 1) for i in range(0, m+1)]
        for i in range(0,m+1):
            dp[i][0] = i
        for j in range(0,n+1):
            dp[0][j] = j
        for i in range(1, m+1):
            for j in range(1,n+1):
                if word1[i-1] == word2[j-1]:
                    dp[i][j] = dp[i-1][j-1]
                else:
                    dp[i][j] = 1 + min(dp[i-1][j-1], dp[i][j-1], dp[i-1][j])
        return dp[m][n]