package Leetcode.DynamicProgramming;

/**
 * Solution for LeetCode problem: 70. Climbing Stairs
 * @author zhengstars
 * @date 2024/08/02
 */
public class ClimbingStairs {
    /**
     * Calculates the number of distinct ways to climb n stairs
     * @param n the number of stairs
     * @return the number of distinct ways to climb the stairs
     */
    public static int climbStairs(int n) {
        // Base case: if n is 0 or 1, there's only one way to climb
        if(n <= 1){
            return 1;
        }

        // Initialize variables for the first two steps
        int prev = 1, curr = 1;

        // Iterate from 2 to n, calculating the number of ways for each step
        for (int i = 2; i <= n; i++) {
            // Calculate the next number in the sequence
            int next = prev + curr;
            // Update prev and curr for the next iteration
            prev = curr;
            curr = next;
        }

        // Return the final result, which represents the number of ways to climb n stairs
        return curr;
    }

    /**
     * Main method for testing the climbStairs function
     */
    public static void main(String[] args) {
        // Test case 1: 2 stairs
        System.out.println("Number of ways to climb 2 stairs: " + climbStairs(2));

        // Test case 2: 3 stairs
        System.out.println("Number of ways to climb 3 stairs: " + climbStairs(3));
    }
}