// Problem Genetic Code // Algorithm Backtracking // Runtime O(3^n) // Author Walter Guttmann // Date 12.03.2003 #include #include #include #include using namespace std; ifstream in("genetic.in"); char s[8192], *end=s, *target=s+5000; bool isThue() { for (int len=1 ; end-len-len>=s ; len++) if (strncmp(end-len-len, end-len, len) == 0) return false; return true; } bool backtrack() { if (end == target) return true; ++end; for (end[-1]='N' ; end[-1]<='P' ; end[-1]++) if (isThue() && backtrack()) return true; --end; return false; } int main() { backtrack(); int n; while (in >> n) { if (n == 0) break; assert(1 <= n && n <= 5000); cout.form("%.*s\n", n, s); } return 0; }