LeetCode 丢失的数字

1. 做差法：

class Solution {
    public int missingNumber(int[] nums) {
        int n = nums.length;
        int cur = 0, sum = n * (n + 1) / 2;
        for (int i : nums) cur += i;
        return sum - cur;
    }
}

2. 异或法：

class Solution {
    public int missingNumber(int[] nums) {
        int n = nums.length;
        int ans = 0;
        for (int i = 0; i <= n; i++) ans ^= i;
        for (int i : nums) ans ^= i;
        return ans;
    }
}