Close fd only when fd >= 0
Close fd only when fd >= 0

lylei/dfs,yvxiang/dfs,yvxiang/coverage_for_bfs,yvxiang/dfs,linyvxiang/dfs,lylei/dfs,yvxiang/coverage_for_bfs,baidu/bfs,baidu/bfs,lylei/dfs,linyvxiang/dfs,yvxiang/dfs,bluebore/dfs,bluebore/bfs,bluebore/dfs,bluebore/dfs,yvxiang/coverage_for_bfs,yvxiang/coverage_for_bfs,baidu/bfs,baidu/bfs,yvxiang/dfs,linyvxiang/dfs,bluebore/bfs,bluebore/bfs,lylei/dfs