class Solution {
    public int climbStairs(int n) {
        int[] dp = new int[n + 1];
        int[] weight = {1,2};
        dp[0] = 1;

        for (int i = 0; i <= n; i++) {
            for (int j = 0; j < weight.length; j++) {
                if (i >= weight[j]) dp[i] += dp[i - weight[j]];
            }
        }

        return dp[n];
    }
}

class Solution {
    public int coinChange(int[] coins, int amount) {
        int max = Integer.MAX_VALUE;
        int[] dp = new int[amount + 1];

        for (int j = 0; j < dp.length; j++) {
            dp[j] = max;
        }

        dp[0] = 0;
        for (int i = 0; i < coins.length; i++) {
            for (int j = coins[i]; j <= amount; j++) {
                if (dp[j - coins[i]] != max) {
                    dp[j] = Math.min(dp[j], dp[j - coins[i]] + 1);
                }
            }
        }
        return dp[amount] == max ? -1 : dp[amount];
    }
}

class Solution {
    public int numSquares(int n) {
        int max = Integer.MAX_VALUE;
        int[] dp = new int[n + 1];
        for (int j = 0; j <= n; j++) {
            dp[j] = max;
        }

        dp[0] = 0;

        for (int j = 1; j <= n; j++) {
            for (int i = 1; i * i <= j; i++) {
                dp[j] = Math.min(dp[j], dp[j - i * i] + 1);
            }
        }
        return dp[n];
    }
}