Sequence differences¶
You are given a sequence of \(n\) integers. Your task is to see if calculating the absolute values of the differences between each pair of consecutive elements of the sequence will yield all numbers from \(1\) to \(n-1\) inclusive.
Source: https://onlinejudge.org/external/100/10038.pdf
Specification¶
Input¶
- \(n\) - natural number from the interval \([1,3000]\)
- \(tab[n]\) - sequence of \(n\) integers
Output¶
- "YES" if the sequence meets the requirement described above, or "NO" otherwise
Example 1¶
Input¶
Output¶
Info
Explanation¶
Let's look at the absolute values of the differences between adjacent elements of the sequence:
- \(|1-4|=3\)
- \(|4-2|=2\)
- \(|2-3|=1\)
As you can see, we obtained all values in the interval \([1,n-1]\), that is, in the interval \([1,3]\).
Example 2¶
Input¶
Output¶
Info
Explanation¶
Let's look at the absolute values of the differences between adjacent elements of the sequence:
- \(|1-4|=3\)
- \(|4-2|=2\)
- \(|2-(-1)|=3\)
- \(|-1-6|=7\)
As you can see, we did not get all the values in the interval \([1,n-1]\), that is, in the interval \([1,4]\)