leetcode_28题——Implement strStr()（采用KMP算法，还没AC，但自己这边测试无误）

Implement strStr()

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Question Solution

Implement strStr().

Returns the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.

Update (2014-11-02):
The signature of the function had been updated to return the index instead of the pointer. If you still see your function signature returns a char * or String, please click the reload button  to reset your code definition.

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这道题是典型的KMP算法的字符串匹配的问题，但不知怎么了就是没AC，先计算匹配值，再采用KMP算法，可能是在计算匹配值时我用的法子太复杂了

所以导致超时间了

#include <iostream>
#include <string>
#include <vector>
using namespace std;

/*"前缀"和"后缀"的最长的共有元素的长度*/
int public_str(string str)
{
	if(str.size()==1||str.size()==0)
		return 0;
	int i=1,len=str.size();
	for(i=1;i<len;i++)
	{
		int flag=0;
		for(int j=0;j<i;j++)
		{
			if(str[j]!=str[len-i+j])
			{
				flag=1;
				break;
			}
		}
		if(flag==0)
			return i;
	}
	return 0;
}

/*计算部分匹配值*/
vector<int> match_value(string str)
{
	vector<int> temp;
	int len=str.size();
	for(int i=0;i<len;i++)
	{
		string str1=str.substr(0,i+1);
		temp.push_back(public_str(str1));
	}
	return temp;
}

/*KMP算法的主要部分*/
int strStr(string haystack, string needle) {
	if(haystack.size()==0||needle.size()==0)
		return -1;
	if(needle.size()>haystack.size())
		return -1;
	vector<int> matchvalue=match_value(needle);
	int len_haystack=haystack.size();
	int len_needle=needle.size();
	int i=0;
	while(i<=(len_haystack-len_needle))
	{
		int flag=0;
		int noMatch=0;
		int j=0;
		for(j=0;j<len_needle;j++)
		{
			if(needle[j]!=haystack[i+j])
			{
				flag=1;
				noMatch=j;
				break;
			}
		}
		if(flag==0)
		{
			return i;
		}
		else if(flag==1)
		{
			if(j==0)
				i=i+1;
			else
				i=i+j-matchvalue[j-1];
		}
	}
	return -1;
}
int main()
{
	string str="ABGTYDFSDFRTGAAASEDF";
	string str1="TYD";
	cout<<strStr(str,str1)<<endl;

}