刷题之Implement strStr()、Climbing Stairs

 public class Solution {
     public int strStr(String haystack, String needle) {
         int big = haystack.length();
         int sub = needle.length();
         if(big==0 && sub==0) return 0;
         if(big==0 && sub!=0) return -1;
         int index = big-sub;
         for(int i=0;i<=index;i++){
             if(haystack.substring(i,sub+i).equals(needle))return i;
         }
         return -1;
     }
 }

是int index = haystack.indexOf(needle)的另一种做法

Climbing Stairs

1）递归调用（容易内存溢出）：

 public class Solution {
     public int climbStairs(int n) {
         if(n<1)return 0;
         if(n==1)return 1;
         if(n==2)return 2;
         return climbStairs(n-1)+climbStairs(n-2);
     }
 }

2）类似斐波那契数列，开头1,2.代替1.1

 public class Solution {
     public int climbStairs(int n) {
         if(n<1)return 0;
         if(n==1)return 1;
         if(n==2)return 2;
         int nums = 0;
         int one = 1;
         int two = 2;
         for(int i=3;i<=n;i++){
             nums = one+two;
             one = two;
             two = nums;
         }
         return nums;
     }
 }

https://leetcode.com/problems/climbing-stairs/#/description