[Leetcode]-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?

Hide Tags： Dynamic Programming

题目：爬楼梯，需要爬到第N步，每次你可以爬层2步或者1步，问总共有几种方法？

思路：Dynamic Programming（动态规划）

//DP(Dynamic Programming) algorithms 见算法导论
//S
 = S[n-1] + S[n-2] ; 
//S[1] = 1 ;
//S[2] = 2 ;
int climbStairs(int n) {
    if( n == 0) return 0;
    if( n == 1) return 1;
    if( n == 2) return 2;

    int one_step = 1;
    int two_step = 2;

    int sum_ways = 0;
    int i = 0 ;
    for(i=2;i<n;i++)
    {
        sum_ways = one_step + two_step;
        one_step = two_step;
        two_step = sum_ways;
    }

    return sum_ways;
}