在计算机科学中,最长公共子串问题是寻找两个或多个已知字符串最长的子串。此问题与最长公共子序列问题的区别在于子序列不必是连续的,而子串却必须是。链接: 百度百科
The Feynman Algorithm:
给定两个字符串T1和T2, 假设dp(i, j)表示T1,T2在位置i, j的公共子串的长度【向位置0的方向,连续相同的字符的数量】
比如“abcdefg”, “absecde”
dp(0,0) = 1 ‘a’ == ‘a’
dp(1,1) = 2 ‘ab’ == ‘ab’
dp(1,2) = 0 ‘b’ != ‘s’
总结规律:
if T1[i] == T2[j] :
dp(i,j) = dp(i-1,j-1) + 1
else:
dp(i,j) = 0
def getLcs(t1:str, t2:str)->str:'''get the longest common substring of two given string'''if not t1:return t1if not t2:return t2# dp = [[0 for i in range(len(t2)+1)] for j in range(len(t1)+1)]max_len = 0dp = [[0 for i in range(len(t2)+1)] for j in range(2)]for i in range(1, len(t1)+1):ind = [0,1][i%2==0]for j in range(1, len(t2)+1):if t1[i-1]==t2[j-1]:dp[ind][j] = dp[1-ind][j-1] + 1else:dp[ind][j] = 0if dp[ind][j] >max_len:max_len = dp[ind][j]p = iprint("max_len:%d , pos: %d"%(max_len,p))return t1[p-max_len:p]