PAT 1092. To Buy or Not to Buy(STL)

CODE:

#include<cstdio>
#include<cstring>
#include<set>
using namespace std;

multiset<char> mst;
char s1[1005],s2[1005];

int main()
{
    while(scanf("%s%s",s1,s2)==2)
    {
        mst.clear();
        bool flag=true;
        int cnt=0;
        int len1=strlen(s1);
        int len2=strlen(s2);
        for(int i=0;i<len1;i++)
        {
            mst.insert(s1[i]);
        }
        multiset<char>::iterator it;
        for(int i=0;i<len2;i++)
        {
            it=mst.find(s2[i]);
            if(it==mst.end())
            {
                flag=false;
                cnt++;
            }
            else
                mst.erase(it);
        }
        if(flag)
            printf("Yes %d\n",mst.size());
        else
            printf("No %d\n",cnt);
    }
    return 0;
}