LeetCode_Edit Distance

Given two words word1 and word2, find the minimum number of steps required to convert word1 to word2. (each operation is counted as 1 step.)

You have the following 3 operations permitted on a word:

a) Insert a character
b) Delete a character
c) Replace a character

int minDistance(string s1, string s2)
{
	int len1 = s1.length();
    int len2 = s2.length();
    if (len1 == 0)
        return len2;
    if (len2 == 0)
        return len1;
        
    int **f = new int *[len1 + 1];
    for (int i = 0; i <= len1; ++i)
    {
        f[i] = new int[len2 + 1];
    }
    // 初始化 
    for (int i = 0; i <= len1; ++i)
    {
		f[i][0] = i;
    }
	for (int j = 0; j <= len2; ++j)
    {
		f[0][j] = j;
    }
        
    for (int i = 1; i <= len1; ++i)
    {
        for (int j = 1; j <= len2; ++j)
        {
			if (s1[i-1] == s2[j-1])
			{
				f[i][j] = f[i-1][j-1];
			}
			else
			{
                int tmp = f[i-1][j-1];
                tmp = min(f[i-1][j], tmp);
                tmp = min(f[i][j-1], tmp);
				f[i][j] = tmp + 1;
            }            
        }
    }
    int ans = f[len1][len2];
    for (int i = 0; i <= len1; ++i)
    {
        delete []f[i];
    }
    delete []f;
    return ans;
}