题目：

解题思路：

        题目中要求元素成数对出现，即每个元素出现偶数次。用哈希表存放每个数出现的次数，再循环查看每个数的次数是否位偶数。

typedef struct {
    int key;
    int count;
    UT_hash_handle hh;
} hashEntry;

bool divideArray(int* nums, int numsSize) {
    hashEntry * cnt = NULL;
    for (int i = 0; i < numsSize; ++i) {
        hashEntry * pEntry = NULL;
        HASH_FIND(hh, cnt, &nums[i], sizeof(int), pEntry);
        if (pEntry == NULL) {
            pEntry = (hashEntry*)malloc(sizeof(hashEntry));
            pEntry -> key = nums[i];
            pEntry -> count = 1;
            HASH_ADD(hh, cnt, key,sizeof(int), pEntry);
        }
        else pEntry -> count++;
    }

    hashEntry *curr = NULL, *next = NULL;
    HASH_ITER(hh, cnt, curr, next)
    {
        if (curr->count % 2 != 0) return false;
    }

    return true;
}