yys130826的博客

class Solution: def countSubstrings(self, s: str) -> int: dp=[[False for _ in range(len(s))] for _ in range(len(s))] res=0 for i in range(len(s)-1,-1,-1):#dp[i][j]由i+1,j-1推出来，所以从左下往右上推。决定了遍历顺序。 for j in range(i,l.