Define <code>dp[i][j]</code> as the minimum count of letter changes needed to split the suffix of string <code>s</code> starting from <code>s[i]</code> into <code>j</code> valid parts.

We have <code>dp[i][j] = min(dp[x + 1][j - 1] + v[i][x])</code>. Here <code>v[i][x]</code> is the minimum number of letter changes to change substring <code>s[i..x]</code> into semi-palindrome.

<code>v[i][j]</code> can be calculated separately by <b>brute-force</b>. We can create a table of <code>v[i][j]</code> independently to improve the complexity. Also note that semi-palindrome’s length is at least <code>2</code>.