function missingNumber(nums){
 const n=nums.length;
 let sum=0;
 for(const x of nums) sum+=x;
 return n*(n+1)/2 - sum;
}
console.log(missingNumber([3,0,1]));

function missingNumber(nums:number[]):number{
 const n=nums.length;
 let sum=0;
 for(const x of nums) sum+=x;
 return (n*(n+1))/2 - sum;
}
console.log(missingNumber([3,0,1]));

package main

func missingNumber(nums []int) int {
	n := len(nums)
	sum := 0
	for _, x := range nums {
		sum += x
	}
	return n*(n+1)/2 - sum
}

func main() {}

fn missing_number(nums: &[i32]) -> i32 {
	let n = nums.len() as i32;
	let sum: i32 = nums.iter().sum();
	n * (n + 1) / 2 - sum
}
fn main() {}

function missingNumberXor(nums){
 let res=nums.length;
 for(let i=0;i<nums.length;i++) res ^= i ^ nums[i];
 return res;
}

function missingNumberXor(nums:number[]):number{
 let res=nums.length;
 for(let i=0;i<nums.length;i++) res ^= i ^ nums[i];
 return res;
}

package main

func missingNumberXor(nums []int) int {
	res := len(nums)
	for i, x := range nums {
		res ^= i ^ x
	}
	return res
}

func main() {}

fn missing_number_xor(nums: &[i32]) -> i32 {
	let mut res = nums.len() as i32;
	for (i, &x) in nums.iter().enumerate() {
		res ^= i as i32 ^ x;
	}
	res
}
fn main() {}