【LeetCode】Climbing Stairs

http://oj.leetcode.com/problems/climbing-stairs/

You are climbing a stair case. It takes n steps to reach to the top.

Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?

递归解法

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

return FClimbStairs(n);

}

private int FClimbStairs(int n) {
// TODO Auto-generated method stub
if(n==1)
return 1;
if(n==2)
return 2;

return FClimbStairs(n-1)+FClimbStairs(n-2);
}
}

非递归解法

public class Solution {
public int climbStairs(int n) {
if(n==0)
return 0;
if(n==1)
return 1;
if(n==2)
return 2;
int[] re = new int[n+1];
re[0]=0;
re[1]=1;
re[2]=2;
for(int i=3;i<n+1;i++){
re[i]=re[i-1]+re[i-2];
}
return re
;

}

}