Compilare: main.cpp: In function 'std::vector<std::vector<int> > shortest_path_all(const std::vector<std::vector<std::pair<int, int> > >&)': main.cpp:13:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < graph.size(); i++) { ~~^~~~~~~~~~~~~~ main.cpp:16:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < graph.size(); i++) { ~~^~~~~~~~~~~~~~ main.cpp:17:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 0; j < graph.size(); j++) { ~~^~~~~~~~~~~~~~ main.cpp:25:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < graph.size(); i++) { ~~^~~~~~~~~~~~~~ main.cpp:26:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 0; j < graph[i].size(); j++) { ~~^~~~~~~~~~~~~~~~~ main.cpp:31:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int k = 0; k < graph.size(); k++) { ~~^~~~~~~~~~~~~~ main.cpp:36:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < graph.size(); i++) ~~^~~~~~~~~~~~~~ main.cpp:37:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 0; j < graph[i].size(); j++) { ~~^~~~~~~~~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:76:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < cost_matrix.size(); i++) { ~~^~~~~~~~~~~~~~~~~~~~ main.cpp:77:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 0; j < cost_matrix.size(); j++) { ~~^~~~~~~~~~~~~~~~~~~~ main.cpp:53:39: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("dijkstra.in", "r", stdin); ^ main.cpp:54:41: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("dijkstra.out", "w", stdout); ^ main.cpp:59:26: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &n, &m); ^ main.cpp:68:43: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d%d", &src, &dst, &cost); ^