foo.cc: In function 'int main()':
foo.cc:37:6: warning: unused variable 'pre' [-Wunused-variable]
   37 |  int pre=0;
      |      ^~~
foo.cc:26:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   26 |   scanf("%d",&j);//输入的是父节点
      |   ~~~~~^~~~~~~~~
foo.cc:31:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   31 |   scanf("%d",&color[i]);
      |   ~~~~~^~~~~~~~~~~~~~~~

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