55. Jump Game

Given an array of non-negative integers, you are initially positioned at the first index of the array.

Each element in the array represents your maximum jump length at that position.

Determine if you are able to reach the last index.

Example 1:

Input: [2,3,1,1,4]
Output: true
Explanation: Jump 1 step from index 0 to 1, then 3 steps to the last index.

Example 2:

Input: [3,2,1,0,4]
Output: false
Explanation: You will always arrive at index 3 no matter what. Its maximum
             jump length is 0, which makes it impossible to reach the last index.

　　这个大致解释下题意，每个元素的值代表当前能跳过的最大步数，最终能到达最后一个元素，即可返回true，否则返回false，下面一张图可以表达题干中的两个例子：

　　这里要用贪心算法，后面继续写。