leetcode 28:实现strStr()
int strStr(string haystack, string needle) {
if(needle.size()==0)
return 0;
for(int i=0;i<haystack.size();i++){
int flag=0;
if(needle.size()>(haystack.size()-i))return -1;
if(haystack[i]==needle[0]){
int j=1;
int k=i+1;
for(;j<needle.size()&&k<haystack.size()&&k-i<=needle.size();j++,k++){
if(needle[j]!=haystack[k]){
flag=1;
break;
}
}
if(flag==0&&k-i==needle.size())
return i;
}
}
return -1;
}