LCS 最长公共子子串

与 最长公共子序列类似

只是最长公共子串必须连续 所以只能走斜线！！！！

'''
LCS 最长公共子序列
'''


def LCS_len(x, y):
    m = len(x)
    n = len(y)
    dp = [[0] * (n + 1) for i in range(m + 1)]
    B = [[' '] * (n + 1) for i in range(m + 1)]
    for i in range(1, m + 1):
        for j in range(1, n + 1):
            if x[i - 1] == y[j - 1]:
                dp[i][j] = dp[i - 1][j - 1] + 1
                B[i][j] = 'X'
         
   
    return dp, B


def LCS_str(B, x, i, j):
    if i == 0 or j == 0:
        return
    if B[i][j] == 'X':
        print(x[i - 1])
        LCS_str(B, x, i - 1, j - 1)

    # elif B[i][j] == 'L':
    #     LCS_str(B, x, i - 1, j)
    else:
        
        LCS_str(B, x, i, j - 1)



def main():
    x = 'bab'
    y = 'caba'
    dp, B = LCS_len(x, y)
    LCS_str(B, x, len(x), len(y))
main()