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': main.c:54:21: warning: array subscript has type 'char' [-Wchar-subscripts] node = node->child[ch]; ^ main.c:60:14: warning: array subscript has type 'char' [-Wchar-subscripts] node->child[ch] = 0; ^ main.c: In function 'query': main.c:144:18: warning: array subscript has type 'char' [-Wchar-subscripts] if (node->child[ch]) { ^ main.c:145:22: warning: array subscript has type 'char' [-Wchar-subscripts] node = node->child[ch]; ^ main.c: In function 'prefix': main.c:159:28: warning: array subscript has type 'char' [-Wchar-subscripts] if (ch < 0 || node->child[ch] == 0) ^ main.c:161:18: warning: array subscript has type 'char' [-Wchar-subscripts] if (node->child[ch]) { ^ main.c:162:22: warning: array subscript has type 'char' [-Wchar-subscripts] node = node->child[ch]; ^ main.c: In function 'main': main.c:184:17: warning: unused variable 'buf' [-Wunused-variable] char line[32], buf[32]; ^~~ main.c: In function 'rm': main.c:65:1: warning: control reaches end of non-void function [-Wreturn-type] } ^ main.c: In function 'main': main.c:187:5: warning: ignoring return value of 'freopen', declared with attribute warn_unused_result [-Wunused-result] freopen( "trie.in", "r", stdin ); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ main.c:188:2: warning: ignoring return value of 'freopen', declared with attribute warn_unused_result [-Wunused-result]