Compilare: main.c: In function 'add': main.c:36:18: warning: array subscript has type 'char' [-Wchar-subscripts] if (node->child[ch] == NULL) { ^ main.c:37:18: warning: array subscript has type 'char' [-Wchar-subscripts] node->child[ch] = &mem[alloc_cnt++]; ^ main.c:38:18: warning: array subscript has type 'char' [-Wchar-subscripts] node->child[ch]->parent = node; ^ main.c:41:21: warning: array subscript has type 'char' [-Wchar-subscripts] node = node->child[ch]; ^ main.c: In function 'rm_rec': main.c:55:58: warning: comparison of distinct pointer types lacks a cast if (node->freq == 0 && node->childrenCount == 0 && node != &T) { ^~ main.c: In function 'rm': main.c:74:21: warning: array subscript has type 'char' [-Wchar-subscripts] node = node->child[ch]; ^ main.c:82:14: warning: array subscript has type 'char' [-Wchar-subscripts] node->child[ch] = 0; ^ main.c: In function 'query': main.c:96:18: warning: array subscript has type 'char' [-Wchar-subscripts] if (node->child[ch]) { ^ main.c:97:22: warning: array subscript has type 'char' [-Wchar-subscripts] node = node->child[ch]; ^ main.c: In function 'prefix': main.c:110:28: warning: array subscript has type 'char' [-Wchar-subscripts] if (ch < 0 || node->child[ch] == 0) ^ main.c:112:18: warning: array subscript has type 'char' [-Wchar-subscripts] if (node->child[ch]) { ^ main.c:113:22: warning: array subscript has type 'char' [-Wchar-subscripts] node = node->child[ch]; ^ main.c: In function 'main': main.c:135:17: warning: unused variable 'buf' [-Wunused-variable] char line[32], buf[32]; ^~~ main.c: In function 'rm': main.c:87:1: warning: control reaches end of non-void function [-Wreturn-type] } ^ main.c: In function 'main':