- For every unordered pair of characters <code>(a, b)</code>, the cost of turning <code>a</code> into <code>b</code> is equal to the minimum between: <ul> <li>If <code>i < j</code>, <code>nextCost[i] + nextCost[i + 1] + … + nextCost[j - 1]</code>, and <code>nextCost[i] + nextCost[i + 1] + … + nextCost[25] + nextCost[0] + … + nextCost[j - 1]</code> otherwise.</li> <li>If <code>i < j</code>, <code>prevCost[i] + prevCost[i - 1] + … + prevCost[0] + prevCost[25] + … + prevCost[j + 1]</code>, and <code>prevCost[i] + prevCost[i - 1] + … + prevCost[j + 1]</code> otherwise.</li> </ul> Where <code>i</code> and <code>j</code> are the indices of <code>a</code> and <code>b</code> in the alphabet.

The shift distance is the sum of costs of turning <code>s[i]</code> into <code>t[i]</code>.