foo.cc: In function 'void init()':
foo.cc:18:9: warning: array subscript has type 'char' [-Wchar-subscripts]
   18 |   t[s[i]]++;
      |         ^
foo.cc: In function 'void build()':
foo.cc:59:33: warning: 'p2' may be used uninitialized in this function [-Wmaybe-uninitialized]
   59 |   tree[i].w=tree[p1].w+tree[p2].w;
      |                        ~~~~~~~~~^
foo.cc:59:22: warning: 'p1' may be used uninitialized in this function [-Wmaybe-uninitialized]
   59 |   tree[i].w=tree[p1].w+tree[p2].w;
      |             ~~~~~~~~~^

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