LeetCode: Jump Game II

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.

Your goal is to reach the last index in the minimum number of jumps.

最开始想像jump game I一样用动态规划，发现会超时。

所以想到了用贪心算法。

可以计算每一步可以跳到的最远距离。第一次到达数组末尾时就是最少的steps。时间复杂度为O(n).

 1 public static int jump2 (int[] A) {
 2         if (A.length == 0) return -1;
 3         int steps = 0;
 4         int index = 0;
 5         int last = -1;
 6
 7         while (index < A.length-1) {
 8             int l = index;
 9             for (int i = index; i > last; i--) {
10                 if (i + A[i] > l) l = i + A[i];
11             }
12             if (index == l) return -1;
13             last = index;
14             index = l;
15             steps++;
16         }
17
18         return steps;
19     }

也可以计算，在每个点的时候能跳到的最远的距离。第一次到达末尾时，是最少的steps。

last记录的是上一次能跳到的最远的距离。只有当i超过last的时候，说明已经超过了上一次跳跃的最大距离，是又发生了一次跳跃。所以steps++。

 1 public int jump(int[] A) {
 2         int steps = 0;
 3         int index = 0;
 4         int last = -1;
 5
 6         for (int i = 0; i < A.length; i++) {
 7
 8             if (index >= A.length - 1) {
 9                 break;
10             }
11             if (i > last) {
12                 steps++;
13                 last = index;
14             }
15             if (i + A[i] > index) {
16
17                 index = i + A[i];
18             }
19         }
20
21         return steps;
22     }

转载于:https://www.cnblogs.com/longhorn/p/3603013.html

LeetCode: Jump Game II相关推荐

leetcode jump game ii
题目: Given an array of non-negative integers, you are initially positioned at the first index of the ...
【To Read】LeetCode | Jump Game II（转载）
题目: Given an array of non-negative integers, you are initially positioned at the first index of the ...
【暴力枚举】LeetCode 90. Subsets II
LeetCode 90. Subsets II solution1和2均是利用set的,3和4是不利用set的 Solution1:我的答案迭代法 class Solution { public:v ...
【DFS】LeetCode 52. N-Queens II
LeetCode 52. N-Queens II Solution1:我的答案教科书一样的回溯法 <程序员面试金典>中有一道一毛一样的题啊! class Solution { publi ...
【数字全排列】LeetCode 47. Permutations II
LeetCode 47. Permutations II Solution1:我的答案笨蛋方法:和第46题的思路差不多,把vector换成了set就OK啦~~~ class Solution { p ...
Jump Game/Jump Game II
题目分析 1. Jump Game I和 Jump Game II放在一起做. 2. 一开始还考虑是不是要用动态规划来解答,因为看上去非常像是要动态规划的,但是后来考虑觉得用贪心的思路来做就可以了.我 ...
Jump Game Jump Game II
Jump Game 解法:贪心+状态记录 class Solution {public boolean canJump(int[] nums) {int index=0;for(int i=0;i&l ...
LeetCode Jump Game Jump GameII
LeetCode Jump Game && Jump GameII 又是每日LeetCode Time, 这里直接解决Jump Game和Jump GameII; 先上题目: Jump ...
[LeetCode] Word Break II 拆分词句之二
[LeetCode] Word Break II 拆分词句之二 Given a string s and a dictionary of words dict, add spaces in s to ...

LeetCode: Jump Game II

LeetCode: Jump Game II相关推荐

最新文章

热门文章