LeetCode70-爬楼梯

LeetCode70-爬楼梯

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public int climbStairs(int n) {
    if(n <= 0) return 0;
    if(n == 1) return 1;
    if(n == 2) return 2;

    int one_step_before = 2;
    int two_steps_before = 1;
    int all_ways = 0;

    for(int i=2; i<n; i++){
        all_ways = one_step_before + two_steps_before;
        two_steps_before = one_step_before;
        one_step_before = all_ways;
    }
    return all_ways;
}