动态规划509|70|746

509斐波那契数

class Solution:
    def fib(self, n: int) -> int:
        if n <= 1:
            return n
        dp = [0] * (n + 1)
        dp[0] = 0
        dp[1] = 1
        for i in range(2, len(dp)):
            dp[i] = dp[i - 1] + dp[i - 2]
        return dp[n]

70爬楼梯

class Solution:
    def climbStairs(self, n: int) -> int:
        if n == 1:
            return n
        dp = [0] * (n + 1)
        dp[1] = 1
        dp[2] = 2
        for i in range(3, len(dp)):
            dp[i] = dp[i - 2] + dp[i - 1]
        return dp[n]

746使用最小花费爬楼梯

class Solution:
    def minCostClimbingStairs(self, cost: List[int]) -> int:
        dp = [0] * (len(cost) + 1)
        dp[0] = 0
        dp[1] = 0
        for i in range(2, len(dp)):
            dp[i] = min(dp[i - 2] + cost[i - 2], dp[i - 1] + cost[i - 1])
        return dp[-1]