题目：

题解：

struct HashTable {
    char key;
    char val;
    UT_hash_handle hh;
};

bool isIsomorphic(char* s, char* t) {
    struct HashTable* s2t = NULL;
    struct HashTable* t2s = NULL;
    int len = strlen(s);
    for (int i = 0; i < len; ++i) {
        char x = s[i], y = t[i];
        struct HashTable *tmp1, *tmp2;
        HASH_FIND(hh, s2t, &x, sizeof(char), tmp1);
        HASH_FIND(hh, t2s, &y, sizeof(char), tmp2);
        if (tmp1 != NULL) {
            if (tmp1->val != y) {
                return false;
            }
        } else {
            tmp1 = malloc(sizeof(struct HashTable));
            tmp1->key = x;
            tmp1->val = y;
            HASH_ADD(hh, s2t, key, sizeof(char), tmp1);
        }
        if (tmp2 != NULL) {
            if (tmp2->val != x) {
                return false;
            }
        } else {
            tmp2 = malloc(sizeof(struct HashTable));
            tmp2->key = y;
            tmp2->val = x;
            HASH_ADD(hh, t2s, key, sizeof(char), tmp2);
        }
    }
    return true;
}