**Consecutive Ones - Amazon Top Interview Questions**

### Problem Statement :

You are given a list of integers nums which contains at least one 1. Return whether all the 1s appear consecutively. Constraints 1 ≤ n ≤ 100,000 where n is the length of nums Example 1 Input nums = [0, 1, 1, 1, 2, 3] Output True Explanation All the 1s appear consecutively here in the middle.

### Solution :

` ````
Solution in C++ :
bool solve(vector<int>& nums) {
for (int i = 0, prev = -1; i < nums.size(); i++) {
if (nums[i] == 1) {
if (prev != -1 && i - prev > 1)
return false;
else
prev = i;
}
}
return true;
}
```

` ````
Solution in Java :
import java.util.*;
class Solution {
public boolean solve(int[] nums) {
int f = -1;
int l = -1;
int c = 0;
for (int i = 0; i < nums.length; i++) {
if (nums[i] == 1) {
if (f == -1) {
f = i;
}
l = i;
c++;
}
}
return (c == l - f + 1);
}
}
```

` ````
Solution in Python :
class Solution:
def solve(self, nums):
alreadyseen = 0
"""
0 means never seen
1 means currently seeing
2 means has finished seeing
"""
for x in nums:
if x == 1:
if alreadyseen == 2:
return False
alreadyseen = 1
elif alreadyseen:
alreadyseen = 2
return True
```

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