Implement strStr()
Implement strStr().
Returns a pointer to the first occurrence of needle in haystack,
or null if needle is not part of haystack.
标准KMP算法。可参考下文。
http://blog.csdn.net/yaochunnian/article/details/7059486
核心思想在于求出模式串前缀与后缀中重复部分，将重复信息保存在next数组中。
class Solution
{
public:
int getlen(char *str)
{
int i;
for(i = 0; str[i] != ‘\0‘; i ++)
;
return i;
}
void getnext(char *str, int len, int next[])
{
int i = 0;
next[i] = -1;
int j = -1;while(i < len-1)
{
if(j==-1 || str[i]==str[j])
{
i++;
j++;
if(str[i] == str[j])
next[i] = next[j];
else
next[i] = j;
}
else
j = next[j];
}
}char *strStr(char *haystack, char *needle)
{
int hlen = getlen(haystack);
//cout << "hlen:" << hlen << endl;
int nlen = getlen(needle);
//cout << "nlen:" << nlen << endl;int *next = new int[nlen];
getnext(needle, nlen, next);int i = 0;
int j = 0;
while(i != hlen && j != nlen)
{
if(j == -1 || haystack[i] == needle[j])
{
i++;
j++;
}
else
{
j = next[j];
}
}
if(j == nlen)
return &haystack[i-nlen];
else
return NULL;
}
};
【LeetCode】Implement strStr(),布布扣,bubuko.com