zoukankan      html  css  js  c++  java
  • LeetCode 45. 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.

    For example:
    Given array A = [2,3,1,1,4]

    The minimum number of jumps to reach the last index is 2. (Jump 1 step from index 0 to 1, then 3 steps to the last index.)

    Note:
    You can assume that you can always reach the last index.

    如果从后往前想,即用递归的思想来思考,会得到比较差的算法,时间复杂度会达到O(n^2)

    如果从前往后想,就会想到时间复杂度为O(n)的算法,设置d[i]代表到达i位置需要的跳数,每个d[i]只修改一次,所以是O(n)的时间复杂度。该思想有点类似于BFS

    这里采用的是O(n)的空间复杂度,还可以继续优化到O(1)的空间复杂度

     1 int d[1000000]={0};
     2 int jump(int* nums, int numsSize) {
     3     if(numsSize==1)return 0;
     4     int hasNumPlace=0;
     5     int endPlace=0;
     6     for(int i=0;i<numsSize-1;i++){
     7         if(i+nums[i]>numsSize-1) //out of nums range
     8             endPlace=numsSize-1;
     9         else 
    10             endPlace=i+nums[i];
    11         
    12         for(int j=hasNumPlace+1;j<=endPlace;j++){
    13             d[j]=d[i]+1;
    14         }
    15        
    16         if(hasNumPlace<i+nums[i])
    17             hasNumPlace=i+nums[i];
    18         if(hasNumPlace==numsSize-1)
    19             break;
    20     }
    21     return d[numsSize-1];
    22 }
  • 相关阅读:
    pcie dma
    Virtual Network
    hashcode与equals
    java四类八种基本数据类型
    jdk 1.7 LinkedList 源码分析
    jdk 1.7 ArrayList 源码分析
    httpclient发送xml字符串(推送)
    HttpClient使用Post和Get提交参数
    httpClient发送Json请求,结果返回Json.
    HttpClient
  • 原文地址:https://www.cnblogs.com/gremount/p/6658960.html
Copyright © 2011-2022 走看看