nums[i] != i
class Solution {
public int missingNumber(int[] nums) {
Arrays.sort(nums);
int low = 0;
int high = nums.length-1;
while(low <= high) {
int mid = (low + high) / 2;
if(nums[mid] == mid){
low = mid + 1;
} else {
high = mid - 1;
}
}
return low;
}