LeetCode/268.cpp at master · nitin-maharana/LeetCode · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
/*
 * Written by Nitin Kumar Maharana
 * nitin.maharana@gmail.com
 */

//Using XOR.
class Solution {
public:
    int missingNumber(vector<int>& nums) {

        int result = 0;

        for(int i = 1; i <= nums.size(); i++)
            result ^= (i ^ nums[i-1]);

        return result;
    }
};

//Using Summation.
class Solution {
public:
    int missingNumber(vector<int>& nums) {
        int len = nums.size();

        int wholeSum = (len * (len + 1)) / 2;

        int arraySum = 0;

        for(int i : nums)
            arraySum += i;

        return wholeSum - arraySum;
    }
};

//Using Summation. Optimized
class Solution {
public:
    int missingNumber(vector<int>& nums) {

        int result = 0;

        for(int i = 1; i <= nums.size(); i++)
            result += (i-nums[i-1]);

        return result;
    }
};