Given an array of integers, each element represents the max number of jumps that you can move forward.
Write a piece of code to find out the minimum number of elements you need to select to reach the end of the array (starting from the first element).
• All integers is equal to or greater than 0
• If an element is 0, you cannot make any jumps
• -1 should be output if it is unable to reach the end of the array
Here is an example to illustrate the question.
Sample Input: 1,3,5,2,9,3,1,1,8
Sample Output: 3
Explanation:
Here the min # of selections is : 3
with the sequence : 1-> 3 -> 9 ->8
First element is 1, so can only go to 3.

Second element is 3, so can make at most 3 jumps: eg to 5 or 2 or 9.

Another example:
Input: 1, 0
Ouput: -1
Explanation: the first element is 1, so can only go to 0. Then can not make any jumps, so we can not reach the end of the array.

#include <iostream>
using namespace std;

int walk(int *arr, int len);

int walk(int *arr, int len)
{
	if (len <=0)
	{
		return 0;
	}
	if(*arr <= 0)
	{	
		return -1;
	}
	//print the element indicating the max steps we can take
	cout<<*arr<<" ";
	//we can reach the end of array by this element
	if(len == 1 || *arr > len-1)
	{
		return 1;
	}
	int max_step = *arr;
	//this array has at least two elements
	//we suppose the nearest element can proceed further
	int *pos = arr+1;
	int *p;
	for (p = arr+2; p<=arr+max_step; p++)
	{
		//if the next element can proceed further, then mark the position.
		if (*p > *pos-(p-pos))
		{
			pos = p;
		}
	}
	int steps = walk(pos, len-(pos-arr));
	if (steps == -1)
	{
		return -1;//we can never reach the end
	}
	else
	{
		return 1+steps;//increment the steps
	}
}


int main()
{
	int arr[] = {1,3,5,2,4,3,1,2,0,0};
	int steps = walk(arr, sizeof(arr)/sizeof(int));
	cout<<endl<<"the steps:"<<steps<<endl;
	return 0;
}