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?
斐波那契数列。
利用DP的方法,一个台阶的方法次数为1次,两个台阶的方法次数为2个。n个台阶的方法可以理解成上n-2个台阶,然后2步直接上最后一步;或者上n-1个台阶,再单独上一步。
公式是S[n] = S[n-1] + S[n-2] S[1] = 1 S[2] = 2
1 class Solution { 2 public: 3 int climbStairs(int n) { 4 if(n==0)return 0; 5 if(n==1)return 1; 6 7 int i; 8 i=1; 9 int tmp=1; 10 int sum=1; 11 int cur=1; 12 while(i<n) 13 { 14 tmp=sum+cur; 15 sum=cur; 16 cur=tmp; 17 i++; 18 } 19 20 return cur; 21 } 22 };