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;}