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?
从后往前求解问题，相当于一维动态规划，但是可以不用数组保存。递推公式与斐波那契额数列类似。public int climbStairs(int n) { if (n == 0 || n == 1) { return n; } int a = 1; int b = 2; int c; for (int i = 3; i <= n; i++) { c = a + b; a = b; b = c; } return b; }
Climbing Stairs,布布扣,bubuko.com
原文：http://blog.csdn.net/u010378705/article/details/29632107