foo.cc: In function ‘int dfs(int)’:
foo.cc:6:14: error: expected ‘]’ before ‘;’ token
    6 |         f[x=1;]
      |              ^
      |              ]
foo.cc:6:15: error: expected primary-expression before ‘]’ token
    6 |         f[x=1;]
      |               ^
foo.cc:7:21: error: ‘i’ was not declared in this scope
    7 |         for(int i=1;i<=x/2;i++)f[x]=dfs(i);
      |                     ^