HackMD
55.Jump Game
tags: Medium,Array,DP,Greedy
題目描述
You are given an integer array nums. You are initially positioned at the array's first index, and each element in the array represents your maximum jump length at that position.
Return true if you can reach the last index, or false otherwise.
範例
Example 1:
Input: nums = [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: nums = [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.
Constraints:
- 1 <=
nums.length<= 104 - 0 <=
nums[i]<= 105
解答
Javascript
function canJump(nums) {
let max = nums[0];
for (let i = 1; i < nums.length; i++) {
if (i > max) return false;
max = Math.max(max, i + nums[i]);
}
return true;
}
Marsgoat Dec 26, 2022
Python
class Solution:
def canJump(self, nums: List[int]) -> bool:
last = len(nums) - 1
for i, num in reversed(list(enumerate(nums))):
if i + num >= last:
last = i
return last == 0
來點反向思維
Yen-Chi ChenMon, Dec 26, 2022
class Solution:
def canJump(self, nums: List[int]) -> bool:
n = len(nums)
#can_reach_end = [0]*len(nums)
#can_reach_end[-1] = 1
last_can_reach = n-1
for idx in range(n-2, -1, -1):
if idx+nums[idx] >= last_can_reach:
#can_reach_end = 1
last_can_reach = idx
if last_can_reach != 0:
return False
else:
return True
一開始寫DFS 笑死 越想越不對勁
玉山Mon, Dec 26, 2022
