Edit Distance.cpp

/*
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
*/

class Solution {
public:
    int minDistance(string word1, string word2) {
        int m = word1.size(), n = word2.size();
        vector<int> pre(n + 1, 0), cur(n + 1, 0);
        for (int j = 1; j <= n; j++) {
            pre[j] = j;
        }
        for (int i = 1; i <= m; i++) {
            cur[0] = i;
            for (int j = 1; j <= n; j++) {
                if (word1[i - 1] == word2[j - 1]) {
                    cur[j] = pre[j - 1];
                } else {
                    cur[j] = min(pre[j - 1], min(cur[j - 1], pre[j])) + 1;
                }
            }
            fill(pre.begin(), pre.end(), 0);
            swap(pre, cur);
        }
        return pre[n];
    }
};