Fix LCP calculation in suffix array implementation

Author: lrvideckis

library/strings/suffix_array/suffix_array_short.hpp

@@ -30,7 +30,7 @@ auto sa_short(const auto& s) {
         sa_inv[sa[i + 1]]++;
         rep (k, 0, K) {
           if (f(sa[i + 1])[k] != f(sa[i])[k]) {
-            lcp[i] = j * k + (sa[i] + j * k < n ? y[sa_inv[sa[i] + j * k]] : 0);
+            lcp[i] = j * k + (sa[i] + j * k < n ? y[x[sa[i] + j * k]] : 0);
           }
         }
       } else {