代码随想录算法训练营第五十四天丨392. 判断子序列、115. 不同的子序列

 392. 判断子序列

动规解法。

class Solution:
    def isSubsequence(self, s: str, t: str) -> bool:
        n1, n2 = len(s), len(t)
        dp = [[0] * (n2 + 1) for _ in range(n1 + 1)]
        for i in range(1, n1 + 1):
            for j in range(1, n2 + 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[n1][n2] == n1

115. 不同的子序列

class Solution:
    def numDistinct(self, s: str, t: str) -> int:
        n1, n2 = len(s), len(t)
        dp = [[0] * (n2 + 1) for _ in range(n1 + 1)]
        for i in range(0, n1 + 1):
            dp[i][0] = 1
        for i in range(1, n1 + 1):
            for j in range(1, n2 + 1):
                if s[i - 1] == t[j - 1]:
                    dp[i][j] = dp[i - 1][j - 1] + dp[i - 1][j]
                else:
                    dp[i][j] = dp[i - 1][j]
        return dp[n1][n2]

今日总结：

对删除这一概念还不是很明白。