题目：

法一 

bool checkIfPangram(char* sentence) {int str[256];memset(str, 0, sizeof(int));for (int i = 0; i < strlen(sentence); ++i) {++str[ sentence[i] ];}for (int j = 'a'; j <= 'z'; ++j) {if (!str[j]) return false;}return true;
}

法二 动态分配

typedef struct {char word;int count;UT_hash_handle hh;
} hashEntry;bool checkIfPangram(char* sentence) {hashEntry * cnt = NULL;for (int i = 0; i < strlen(sentence); i++) {hashEntry* pEntry = NULL;HASH_FIND(hh, cnt, &sentence[i], sizeof(char), pEntry);if (pEntry == NULL) {hashEntry * pEntry = (hashEntry*)malloc(sizeof(hashEntry));pEntry -> word = sentence[i];pEntry -> count = 1;HASH_ADD(hh, cnt, word, sizeof(char), pEntry);}else pEntry -> count++;}hashEntry *curr = NULL, *next = NULL;int num = 26;HASH_ITER(hh, cnt, curr, next){if (curr -> count > 0) {num--;}if (num == 0) return true;free(curr);}return false;
}