2013.12.22 04:13
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?
Solution:
Search for "Fibonacci sequence" and calculate the nth element in the sequence.
Time complexity is O(n), space complexity is O(1).
Accepted code:
1 class Solution { 2 public: 3 int climbStairs(int n) { 4 // Note: The Solution object is instantiated only once and is reused by each test case. 5 int f1, f2, f3; 6 7 f1 = 0; 8 f2 = 1; 9 10 if(n <= 0){ 11 return 0; 12 } 13 14 for(int i = 0; i < n; ++i){ 15 f3 = f1 + f2; 16 f1 = f2; 17 f2 = f3; 18 } 19 20 return f3; 21 } 22 };