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;
}