public class Solution {
public int climbStairs(int n) {
if (n <= 1) {
return 1;
}
//state
int[] f = new int[n + 1];
//initiate
f[0] = 0;
f[1] = 1;
f[2] = 2;
//function
for (int i = 3; i <= n; i++) {
f[i] = f[i - 1] + f[i - 2];
}
//answer
return f[n];
}
}