leetcode 之Implement strStr()（27）

char *strStr(char *haystack, char*needle)
{
char* p1;
char* p2;
char* p1_advance=haystack;

//当字符串数量不足时，直接停止匹配
for (p2 = &needle[1]; *p2; p2++)
p1_advance++;

for (p1 = haystack; *p1_advance; p1_advance++)
{
char *p1_old = p1;
p2 = needle;
while (*p1 && *p2 && *p1 == *p2)
{
p1++;
p2++;
}
if (!*p2)return p1_old;

p1 = p1_old + 1;
}

return nullptr;
}