leetcode 70. 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?

Note: Given n will be a positive integer.

本质上就是Fibonacci数列（想起了高中数学老师说的菲尔拨拉数列，哈哈哈）
class Solution {
public:
int climbStairs(int n) {
int ways[n + 1];
if(n >= 1) {
ways[1] = 1;
}
if (n >= 2) {
ways[2] = 2;
}
int k = 3;
while(k <= n) {
ways[k] = ways[k - 1] + ways[k - 2];
k++;
}
return ways[n];
}
};

在leetcode上看到一种很有意思的解法。
int climbStairs(int n) {
int a = 1, b = 1;
while (n–)
a = (b += a) - a;
return a;
}

呼呼呼山(http://code4fun.me)
2 May 2017 6:42 PM