**Lone Integer - Amazon Top Interview Questions**

### Problem Statement :

You are given a list of integers nums where each integer occurs exactly three times except for one which occurs once. Return the lone integer. Bonus: solve it in \mathcal{O}(1)O(1) space. Constraints n ≤ 100,000 where n is length of nums Example 1 Input nums = [2, 2, 2, 9, 5, 5, 5] Output 9 Example 2 Input nums = [7, 1, 1, 1] Output 7

### Solution :

` ````
Solution in C++ :
int solve(vector<int>& nums) {
vector<int> bit(32, 0);
for (int i = 0; i < 32; i++) {
for (int& no : nums) {
if ((no >> i) & 1) {
bit[i]++;
}
}
}
int ans = 0;
for (int i = 0; i < 32; i++) {
if (bit[i] % 3 != 0) {
ans |= (1 << i);
}
}
return ans;
}
```

` ````
Solution in Java :
import java.util.*;
class Solution {
public int solve(int[] nums) {
int bit = 1;
int res = 0;
// for each bit digit
for (int i = 0; i < 31; i++) {
int count = 0;
// for every number
for (int n : nums) {
if ((n & bit) != 0)
count += 1;
}
bit = bit << 1;
if (count % 3 == 1)
res += (1 << i);
}
return res;
}
}
```

` ````
Solution in Python :
class Solution:
def solve(self, nums):
ans = 0
for i in range(32):
bit = 0
for j in nums:
if j & 1 << i:
bit += 1
if bit % 3 == 1:
ans |= 1 << i
return ans
```

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