Jump Game 解答

Question

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.

Solution

We apply Greedy Algorithm here to solve the problem. Key to the solution is to check largest distance that every element can reach.

1) when the current position can not reach next position (return false)

2) when the maximum index can reach the end (return true).

 1 public class Solution {
 2     public boolean canJump(int[] nums) {
 3         if (nums == null || nums.length <= 1)
 4             return true;
 5         int max = 0;
 6         for (int i = 0; i < nums.length; i++) {
 7             if (nums[i] == 0 && max <= i)
 8                 return false;
 9             if (i + nums[i] > max)
10                 max = i + nums[i];
11             if (max >= nums.length - 1)
12                 return true;
13         }
14         return false;
15     }
16 }