Sum of Unique Elements
You are given an integer array nums. The unique elements of an array are the elements that appear exactly once in the array.
Return the sum of all the unique elements of nums.
Example 1:
Input: nums = [1,2,3,2]
Output: 4
Explanation: The unique elements are [1,3], and the sum is 4.
Example 2:
Input: nums = [1,1,1,1,1]
Output: 0
Explanation: There are no unique elements, and the sum is 0.
Example 3:
Input: nums = [1,2,3,4,5]
Output: 15
Explanation: The unique elements are [1,2,3,4,5], and the sum is 15.
Constraints:
1 <= nums.length <= 100
1 <= nums[i] <= 100
思路一： 符合条件的 nums[i] 范围在 [1, 100]，用数组做映射
public int sumOfUnique(int[] nums) {
int[] arr = new int[100];
for (int num : nums) {
if (arr[num - 1] > 0) {
arr[num - 1] = -1;
} else if (arr[num - 1] == 0) {
arr[num - 1] = num;
}
}
int result = 0;
for (int i : arr) {
if (i > 0) {
result += i;
}
}
return result;
}