在字符串中查找子字符串

# 定义主字符串和子字符串
main_string = "Hello, World!"
substring = "World"

# 使用find方法查找子字符串
index = main_string.find(substring)

if index != -1:
    print(f"子字符串 '{substring}' 在主字符串中的起始索引是 {index}")
else:
    print(f"子字符串 '{substring}' 不在主字符串中")

def compute_lps(pattern):
    length = 0
    lps = [0] * len(pattern)
    i = 1
    while i < len(pattern):
        if pattern[i] == pattern[length]:
            length += 1
            lps[i] = length
            i += 1
        else:
            if length != 0:
                length = lps[length - 1]
            else:
                lps[i] = 0
                i += 1
    return lps

def kmp_search(pattern, text):
    lps = compute_lps(pattern)
    i = j = 0
    while i < len(text):
        if pattern[j] == text[i]:
            i += 1
            j += 1
        if j == len(pattern):
            print(f"找到匹配，起始索引为 {i - j}")
            j = lps[j - 1]
        elif i < len(text) and pattern[j] != text[i]:
            if j != 0:
                j = lps[j - 1]
            else:
                i += 1

# 使用KMP算法进行查找
kmp_search(substring, main_string)