LeetCode: 55. Jump Game(Week 8)

55. Jump Game

• 题目
  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.	
  

• 解题思路

  • 题意比较简单，给定每一个点能向前跳跃的距离，求是否能从初始位置到末尾位置
  • 思路：使用一个变量maxDis记录当前能访问到最远的节点 ，遍历数组节点时候，需要判断当前节点能否被访问到，如果能访问到，则以该节点能访问到的最远节点i + nums[i]与当前能访问的最远节点maxDis比较，使得maxDis = max(maxDis, i + nums[i](核心状态转移)。如果maxDis >= nums.size() - 1，则证明可以访问到最后一个节点。

• 实现代码

  class Solution {
  public:
  	bool canJump(vector<int>& nums) {
  		int maxDis = 0;
  		int len = nums.size();
  		int i = 0;
  		while(maxDis < len - 1 && maxDis >= i && i < len) {
  			maxDis = max(maxDis, i + nums[i]);
  			++i;
  		}
  		return maxDis >= len - 1;
  	}
  };