leetcode/Problems/0072.cpp at master · DimitrijeDobrota/leetcode · GitHub

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class Solution {
  public:
    int minDistance(string word1, string word2) {
        int n = word1.size(), m = word2.size();
        vector<vector<int>> dp(n + 1, vector<int>(m + 1, 0));
        for (int i = 1; i <= n; i++)
            dp[i][0] = i;
        for (int j = 1; j <= m; j++)
            dp[0][j] = j;

        for (int i = 1; i <= n; i++) {
            for (int j = 1; j <= m; j++) {
                if (word1[i - 1] == word2[j - 1])
                    dp[i][j] = dp[i - 1][j - 1];
                else
                    dp[i][j] = min(dp[i - 1][j - 1], min(dp[i][j - 1], dp[i - 1][j])) + 1;
            }
        }
        return dp.back().back();
    }
};

// Improvement, use two DP arrays instead of a matrix
class Solution {
  public:
    int minDistance(const string &word1, const string &word2) {
        int n = word1.size(), m = word2.size();
        if (n == 0 || m == 0) return max(m, n);
        vector<int> dp1(m + 1, 0), dp2(m + 1, 0);
        iota(dp1.begin(), dp1.end(), 0);
        for (int i = 1; i <= n; i++) {
            dp2[0]++;
            for (int j = 1; j <= m; j++) {
                if (word1[i - 1] == word2[j - 1])
                    dp2[j] = dp1[j - 1];
                else
                    dp2[j] = min({dp1[j - 1], dp2[j - 1], dp1[j]}) + 1;
            }
            dp1 = dp2;
        }
        return dp2[m];
    }
};