ACM模板（4）vector的索引

//根據鍵和索引表(vector或map)得到值

//根據鍵和值得到map索引表

//把v和id轉化爲v[id]
template<typename T>
vector<int> fgetNumFromId(vector<T> &v,vector<int>id)
{
    vector<T>ans;
    ans.resize(id.size());
    for(int i=0;i<id.size();i++)ans[i]= (id[i]>=0 && id[i]<v.size()) ? v[id[i]] : -1;
    return ans;
}
//把v1和v2 轉化成1個map<v1,v2>
template<typename T1,typename T2>
map<T1,T2> vectorToMap(vector<T1> &v1,vector<T2> &v2)
{
    map<T1,T2>m;
    for(int i=0;i<v1.size();i++)m[v1[i]]=v2[i];
    return m;
}
//1個vector加1個map轉化成map[vector]
template<typename T1,typename T2>
vector<T2> vmToVector(vector<T1> &v,map<T1,T2>&m)
{
    vector<T2>ans;
    ans.resize(v.size());
    for(int i=0;i<v.size();i++)ans[i]=m[v[i]];
    return ans;
}