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Climbing Stairs

题目

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?

方法

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;
    }