Compilare: main.cpp: In function 'std::vector<int> join(std::vector<int>, std::vector<int>)': main.cpp:27:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i <= a.size (); i++) ~~^~~~~~~~~~~~ main.cpp:28:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 0; j <= b.size (); j++) ~~^~~~~~~~~~~~ main.cpp:31:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i <= a.size (); i++) ~~^~~~~~~~~~~~ main.cpp:32:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 0; j <= b.size (); j++) { ~~^~~~~~~~~~~~ main.cpp:33:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (i < a.size ()) _ (dp[i + 1][j], dp[i][j] + (i + j + 1) * w[a[i]]); ~~^~~~~~~~~~~ main.cpp:34:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (j < b.size ()) _ (dp[i][j + 1], dp[i][j] + (i + j + 1) * w[b[j]]); ~~^~~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:80:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < order.size (); i++) ~~^~~~~~~~~~~~~~~ main.cpp:62:44: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen ("purification.in", "r", stdin); ^ main.cpp:63:46: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen ("purification.out", "w", stdout); ^