[Swift]LeetCode55. 跳跃游戏 | Jump Game

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.

数组中的每个元素代表你在该位置可以跳跃的最大长度。

判断你是否能够到达最后一个位置。

示例 1:

输入: [2,3,1,1,4]
输出: true
解释: 从位置 0 到 1 跳 1 步, 然后跳 3 步到达最后一个位置。

示例 2:

输入: [3,2,1,0,4]
输出: false
解释: 无论怎样，你总会到达索引为 3 的位置。但该位置的最大跳跃长度是 0 ， 所以你永远不可能到达最后一个位置。

16ms

 1 class Solution {
 2     func canJump(_ nums: [Int]) -> Bool {
 3         var bestPos = 0
 4
 5         var i = nums.count - 1
 6         while (i >= 0 ) {
 7             if (nums[i] + i >= bestPos) {
 8                 bestPos = i
 9             }
10             i -= 1
11         }
12
13         return bestPos == 0
14     }
15 }

 1 class Solution {
 2     func canJump(_ nums: [Int]) -> Bool {
 3         if nums.isEmpty { return true }
 4         var ind = nums.count - 1
 5         for i in (0..<nums.count).reversed() {
 6             if (i + nums[i]) >= ind {
 7                 ind = i
 8             }
 9         }
10         return ind == 0
11     }
12 }

 1 class Solution {
 2     func canJump(_ nums: [Int]) -> Bool {
 3         var maxIndex = nums[0]
 4
 5         for (index, val) in nums.enumerated() {
 6
 7             if index > maxIndex {
 8                 return false
 9             }
10
11             maxIndex = max(maxIndex, index + val)
12         }
13
14         return true
15     }
16 }

 1 class Solution {
 2     func canJump(_ nums: [Int]) -> Bool {
 3         let count = nums.count
 4         if count > 0 {
 5             var index = 1 // 现在检查
 6             var maxIndex = nums.first! // 现在最多去到
 7             if maxIndex >= count - 1 {
 8                 return true
 9             }
10             var newIndex = 0 // 新的最多去到
11
12             while index <= maxIndex {
13                 newIndex = nums[index] + index
14                 if newIndex > maxIndex {
15                     maxIndex = newIndex
16                     if newIndex >= count - 1 {
17                         return true
18                     }
19                 }
20                 index += 1
21             }
22         }
23         return false
24     }
25 }

 1 class Solution {
 2     func canJump(_ nums: [Int]) -> Bool {
 3         var lastPos = 0
 4         for (index, num) in nums.enumerated() {
 5             if index > lastPos {
 6                 return false
 7             }
 8
 9             lastPos = max(lastPos, num + index)
10         }
11
12         return true
13     }
14 }

原文地址：https://www.cnblogs.com/strengthen/p/9917793.html