Climbing Stairs
Link: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?
1 public class Solution { 2 HashMap<Integer, Integer> map = new HashMap<Integer, Integer>(); 3 public int climbStairs(int n) { 4 if (n == 1 || n == 0) 5 return 1; 6 int steps = 0; 7 int step1 = 0; 8 int step2 = 0; 9 //using memorized recursion 10 if (map.containsKey(n - 1)) 11 step1 = map.get(n - 1); 12 else 13 step1 = climbStairs(n - 1); 14 if (map.containsKey(n - 2)) 15 step2 = map.get(n - 2); 16 else 17 step2 = climbStairs(n - 2); 18 steps += step1 + step2; 19 map.put(n - 1, step1); 20 map.put(n - 2, step2); 21 return steps; 22 } 23 }
