从列表中选择子部分相同的最长字符串

def longest_common_substring(str1, str2):
    m, n = len(str1), len(str2)
    dp = [[0] * (n + 1) for _ in range(m + 1)]
    max_length = 0

    for i in range(1, m + 1):
        for j in range(1, n + 1):
            if str1[i - 1] == str2[j - 1]:
                dp[i][j] = dp[i - 1][j - 1] + 1
                max_length = max(max_length, dp[i][j])

    return max_length

# 示例用法
str_list = ["abcdxyz", "xyzabcd", "abcd", "xyz"]
result = longest_common_substring(str_list[0], str_list[1])
print(result)  # 输出结果为4，即"abcd"和"abcd"是列表中选择子部分相同的最长字符串