LeetCode-in-All
70. Climbing Stairs
Easy
You are climbing a staircase. It takes n steps to reach the top.
Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?
Example 1:
Input: n = 2
Output: 2
Explanation: There are two ways to climb to the top.
-
1 step + 1 step
-
2 steps
Example 2:
Input: n = 3
Output: 3
Explanation: There are three ways to climb to the top.
-
1 step + 1 step + 1 step
-
1 step + 2 steps
-
2 steps + 1 step
Constraints:
1 <= n <= 45
Solution
class Solution {
int climbStairs(int n) {
if (n < 2) {
return n;
}
List<int> cache = List.filled(n, 0);
// Initialize the base cases for 0 and 1 steps
cache[0] = 1;
cache[1] = 2;
// Fill the cache with results for each step
for (int i = 2; i < n; i++) {
cache[i] = cache[i - 1] + cache[i - 2];
}
return cache[n - 1];
}
}