101362: [AtCoder]ABC136 C - Build Stairs
Memory Limit:256 MB
Time Limit:2 S
Judge Style:Text Compare
Creator:
Submit:1
Solved:0
Description
Score : $300$ points
Problem Statement
There are $N$ squares arranged in a row from left to right. The height of the $i$-th square from the left is $H_i$.
For each square, you will perform either of the following operations once:
- Decrease the height of the square by $1$.
- Do nothing.
Determine if it is possible to perform the operations so that the heights of the squares are non-decreasing from left to right.
Constraints
- All values in input are integers.
- $1 \leq N \leq 10^5$
- $1 \leq H_i \leq 10^9$
Input
Input is given from Standard Input in the following format:
$N$ $H_1$ $H_2$ $...$ $H_N$
Output
If it is possible to perform the operations so that the heights of the squares are non-decreasing from left to right, print Yes
; otherwise, print No
.
Sample Input 1
5 1 2 1 1 3
Sample Output 1
Yes
You can achieve the objective by decreasing the height of only the second square from the left by $1$.
Sample Input 2
4 1 3 2 1
Sample Output 2
No
Sample Input 3
5 1 2 3 4 5
Sample Output 3
Yes
Sample Input 4
1 1000000000
Sample Output 4
Yes