parks.cpp: In function 'void dfs(int)':
parks.cpp:15:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
15 | for(int i=0;i<v[x].size();i++) {
| ~^~~~~~~~~~~~
parks.cpp: In function 'int construct_roads(std::vector<int>, std::vector<int>)':
parks.cpp:22:3: error: 'build' was not declared in this scope
22 | build({},{},{},{});
| ^~~~~
parks.cpp:29:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<std::pair<int, int>, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
29 | for(int i=0;i<v1.size();i++) {
| ~^~~~~~~~~~
parks.cpp:30:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<std::pair<int, int>, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
30 | for(int j=i+1;j<v1.size() && j-i<=3;j++) {
| ~^~~~~~~~~~
parks.cpp:43:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
43 | for(int i=0;i<u2.size();i++) {
| ~^~~~~~~~~~
parks.cpp:64:5: error: 'build' was not declared in this scope
64 | build(u2,v2,a2,b2);
| ^~~~~