华为（8）查找两个字符串a,b中的最长公共子串

#include <iostream>
#include <string>
using namespace std;
 static string iQueryMaxCommString(string &stringA, string stringB)
 {
     unsigned int lengthA=stringA.length();
     unsigned int lengthB=stringB.length();
     unsigned int counts=0;
     unsigned int pos_end=0;
     for(unsigned int i=0;i<lengthA;++i)
     {
         unsigned int posA=i;
         unsigned int countsA=0;
         for(unsigned int j=0;j<lengthB;++j)
         {
             if(stringA[posA] == stringB[j])
             {
                 ++posA;
                 ++countsA;
                 if(countsA>counts)
                 {
                     counts=countsA;
                     pos_end=posA-1;
                 }
             }
         }
     }
     unsigned int pos_begin=pos_end-counts+1;
     string str;
     for(unsigned int i=pos_begin;i<=pos_end;++i)
     {
         str.push_back(stringA[i]);
     }
     return str;
 }

int main()
{
    string str1,str2;
    getline(cin,str1);
    getline(cin,str2);
    cout<<iQueryMaxCommString(str1,str2)<<endl;
    return 0;
}