Errata of the english translation

Some typos we spotted in the book.

• page 40 Figure 1.8: there should be two different gray shades among the rectangles. In the final print they might be too close to be distinguished.

• page 47, head of section 2.5: the second abra should be aligned with the suffix of the string abracadabra above.

• page 55: In the code of powerstring_by_find, the variables u and x should be the same.

• page 115: the formula should be

\[\frac{d'[n][v] - d'[k][v]}{n-k} = \frac{d[n][v] - n\Delta - (d[k][v] - k\Delta)}{n-k}\\ = \frac{d[n][v] - d[k][v] }{n-k} - \frac{n\Delta - k\Delta}{n-k}\\ = \frac{d[n][v] - d[k][v] }{n-k} - \Delta\]

• page 143: the expression $\sum_{E_\ell}\ell$ should be instead $\sum \ell$, which stands for $\sum_{u\in U} \ell(u) + \sum_{v\in V} \ell(v)$.

• page 213: Indeed, an integer y can be written -> any composite integer y

• page 240, last line: suffix of t begn inning -> beginning