[Explanations] hopscotch

Title Description

Sunday, Xiao Ming finished his homework on his classmates about sport.
They came to a clearing, drew N consecutive squares, each square on a random fill a number, we start from the first grid, every time you can jump back no more than a few of the squares of the current step number, we start this game, the minimum number of steps to see who jump to the last grid.
Xiao Ming as leader of the obviously wanted to win, so he wants you to help him.

Input and output formats

Input formats:

The first line contains an integer N (N <5000), is the number of grid painted;
second line contains N integers representing the number of ai (ai≤1000) on each grid.

Output formats:

Output line, represents the minimum number of hops.

Sample input and output

Sample input:

5
2 3 1 1 1

Sample output:

2
This question is at first glance seems to be back
then timeout
and then found to reverse thinking

From the back to find

From the back to find

After looking forward!

With code:

#include<iostream>
using namespace std;
int n,a[5005],now,step;
int main()
{
    cin>>n;
    for(register int i=1;i<=n;++i) cin>>a[i];
    now=n;
    while(now!=1)
    {
        for(register int i=1;i<=now;++i)
        {
            if(now-i<=a[i])
            {
                now=i;
                ++step;
                break;
            }
        }
    }
    cout<<step;
}