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

Reference

回到題目列表