View Compilation Error

0_0_32279832_29318.cpp: In function 'int Merge(int, int)':
0_0_32279832_29318.cpp:4:5: error: 'tree' was not declared in this scope
  if(tree[x].val < tree[y].val) swap(x, y);  // 大堆
     ^
0_0_32279832_29318.cpp:4:41: error: 'swap' was not declared in this scope
  if(tree[x].val < tree[y].val) swap(x, y);  // 大堆
                                         ^
0_0_32279832_29318.cpp:5:2: error: 'tree' was not declared in this scope
  tree[x].r = Merge(tree[x].r, y);
  ^
0_0_32279832_29318.cpp:7:28: error: 'swap' was not declared in this scope
   swap(tree[x].l, tree[x].r);
                            ^