55. Jump Game，55jumpgame

55. Jump Game，55jumpgame

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.

For example:
A = [2,3,1,1,4], return true.

A = [3,2,1,0,4], return false.

貪心法，每次跳躍一步，可跳步數減去1,如果新的位置步數大於剩余步數，使用新的步數繼續移動，如果可跳步數小於0且還沒到最後一個步數，那麼失敗。

 1 class Solution {
 2 public:
 3     bool canJump(vector<int>& nums) {
 4         if(nums.size() == 0){
 5             return true;
 6         }
 7         
 8         int reach = nums[0];
 9         for(int i = 1; i < nums.size(); i ++){
10             reach--;
11             
12             if(reach < 0){
13                 return false;
14             }
15             
16             if(reach < nums[i]){
17                 reach = nums[i];
18             }
19         }
20         return true;
21     }
22 };