目录

学习目标

学习内容

 392.判断子序列 

  115.不同的子序列  

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学习目标

学习内容

 392.判断子序列 

392. 判断子序列 - 力扣（LeetCode）https://leetcode.cn/problems/is-subsequence/

class Solution:
    def isSubsequence(self, s: str, t: str) -> bool:
        m = len(s)
        n = len(t)
        if m==0:return True
        if m>n or n==0:return False
        dp = [[False]*(n+1) for _ in range(m+1)]
        dp[0] = [True]*(n+1)
        for i in range(1,m+1):
            for j in range(1,n+1):
                dp[i][j] = (s[i-1]==t[j-1] and dp[i-1][j-1]) or dp[i][j-1]
                if i==m and dp[i][j]:return True
            #print(dp)
        return False

  115.不同的子序列  

115. 不同的子序列 - 力扣（LeetCode）https://leetcode.cn/problems/distinct-subsequences/

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