题目：

题解：

typedef struct HashItem {
    int key;
    bool val;
    UT_hash_handle hh;
} HashItem;

bool dfs(int maxChoosableInteger, int usedNumbers, int desiredTotal, int currentTotal, HashItem **memo) {
    HashItem *pEntry = NULL;
    HASH_FIND_INT(*memo, &usedNumbers, pEntry);
    if (NULL == pEntry) {
        bool res = false;
        for (int i = 0; i < maxChoosableInteger; i++) {
            if (((usedNumbers >> i) & 1) == 0) {
                if (i + 1 + currentTotal >= desiredTotal) {
                    res = true;
                    break;
                }
                if (!dfs(maxChoosableInteger, usedNumbers | (1 << i), desiredTotal, currentTotal + i + 1, memo)) {
                    res = true;
                    break;
                }
            }
        }
        pEntry = (HashItem *)malloc(sizeof(HashItem));
        pEntry->key = usedNumbers;
        pEntry->val = res;
        HASH_ADD_INT(*memo, key, pEntry);
    }
    return pEntry->val;
}

bool canIWin(int maxChoosableInteger, int desiredTotal) {
    HashItem *memo = NULL;
    if ((1 + maxChoosableInteger) * (maxChoosableInteger) / 2 < desiredTotal) {
        return false;
    }
    return dfs(maxChoosableInteger, 0, desiredTotal, 0, &memo);
}