Leetcode 刷题笔记1 动态规划part11

leetcode 1143 最长公共子序列

难点在于保持相对顺序

class Solution:
    def longestCommonSubsequence(self, text1: str, text2: str) -> int:
        dp = [[0] * (len(text2) + 1) for i in range(len(text1) + 1)]
        for i in range(1, len(text1) + 1):
            for j in range(1, len(text2) + 1):
                if text1[i - 1] == text2[j - 1]:
                    dp[i][j] = dp[i - 1][j - 1] + 1
                else:
                    dp[i][j] = max(dp[i - 1][j], dp[i][j - 1])
        return dp[-1][-1]

leetcode 1035 不相交的线

同上，求最长公共子序列的变型

class Solution:
    def maxUncrossedLines(self, nums1: List[int], nums2: List[int]) -> int:
        dp = [[0] * (len(nums2) + 1) for _ in range(len(nums1) + 1)]
        for i in range(1, len(nums1) + 1):
            for j in range(1, len(nums2) + 1):
                if nums1[i - 1] == nums2[j - 1]:
                    dp[i][j] = dp[i - 1][j - 1] + 1
                else:
                    dp[i][j] = max(dp[i - 1][j], dp[i][j - 1])
        return dp[-1][-1]

leetcode 53 最大子数组和

class Solution:
    def maxSubArray(self, nums: List[int]) -> int:
        dp = [float('-inf')] * (len(nums) + 1)
        dp[0] = nums[0]
        for i in range(1, len(nums)):
            dp[i] = max(dp[i - 1] + nums[i], nums[i])
        return max(dp) 

leetcode 392 判断子序列

class Solution:
    def isSubsequence(self, s: str, t: str) -> bool:
        dp = [[0] * (len(t) + 1) for _ in range(len(s) + 1)]
        for i in range(1, len(s) + 1):
            for j in range(1, len(t) + 1):
                if s[i - 1] == t[j - 1]:
                    dp[i][j] = dp[i - 1][j - 1] + 1
                else:
                    dp[i][j] = dp[i][j - 1]
        return dp[-1][-1] == len(s)