PAT 甲级 1002 A+B for Polynomials

This time, you are supposed to find A+B where A and B are two polynomials.

Input

Each input file contains one test case. Each case occupies 2 lines, and each line contains the information of a polynomial: K N1 a_N1 N2 a_N2 ... NK a_NK, where K is the number of nonzero terms in the polynomial, Ni and a_Ni (i=1, 2, ..., K) are the exponents and coefficients, respectively. It is given that 1 <= K <= 10，0 <= NK < ... < N2 < N1 <=1000.

Output

For each test case you should output the sum of A and B in one line, with the same format as the input. Notice that there must be NO extra space at the end of each line. Please be accurate to 1 decimal place.

Sample Input

2 1 2.4 0 3.2
2 2 1.5 1 0.5

Sample Output

3 2 1.5 1 2.9 0 3.2

多项式求和，做这道题卡了好久，一开始看输出结果以为是以  coefficients   系数来排序，由于我用的是map来做，结果map不支持对value值进行排序，只能通过放到vector里面进行排序，然而。。。。。

#include <iostream>
#include "cstring"
#include <stdio.h>
#include "iomanip"
#include "vector"
#include "cmath"
#include "stack"
#include "algorithm"
#include <math.h>
#include "map"
using namespace std;
typedef
pair<double,double>PAIR;//由于MAP不是连续的,要使用vector的sort，只能把map改成pair
struct
CmpByValue    //自定义的cmp    
{ bool operator()(const
PAIR&
lhs,
const
PAIR&
rhs)
{
    return
lhs.second
<
rhs.second;


  }


};
int main()
{
 
    int k;
    cin>>k;
    map <double,double>a;

    int i;double n,an;
    for(i=0;i<k;i++)
    {
        cin>>n>>an;
        a[n]+=an;
    }
    cin>>k;
    for(i=0;i<k;i++)
    {
        cin>>n>>an;
        a[n]+=an;
    }
    cout<<a.size()<<" ";
    vector<PAIR>abc(a.begin(),a.end()   );
    sort(abc.begin(),abc.end(),CmpByValue());

    for(i=0;i<abc.size();i++)
    {
        cout<<abc[i].first<<" "<<abc[i].second;
        if(i!=abc.size()-1)
            cout<<" ";
    }
return  0;


}

调了好久没搞出来，去网上搜了一下发现原来是按照exponents 排序，，那就好办了，直接map就行了，map默认是按照key从小到大，用个反转迭代器反向输出把，刚好和答案相反。需要注意一点要对系数进行一个判断合法

#include <iostream>
#include "cstring"
#include <stdio.h>
#include "iomanip"
#include "vector"
#include "cmath"
#include "stack"
#include "algorithm"
#include <math.h>
#include "map"
using namespace std;

int main()
{
 
    int k,q=0;
    cin>>k;
    map <int,double>a;

    int i;double n,an;
    for(i=0;i<k;i++)
    {
        cin>>n>>an;

        a[n]+=an;
    }
    cin>>k;
    for(i=0;i<k;i++)
    {
        cin>>n>>an;

        a[n]+=an;
    }
    int s=0;
    map<int,double> ::reverse_iterator it;
    map<int,double> ::const_iterator ii;
    for(ii=a.begin();ii!=a.end();ii++)
    {
        if(ii->second!=0.0&&ii->second!=-0.0)
           s++;
    }
    cout<<s;
    for( it=a.rbegin();it!=a.rend();it++)
    { if(it->second!=0.0&&it->second!=-0.0)
        cout<<" "<<it->first<<" "<<fixed<<setprecision(1)<<it->second;

    }
    cout<<endl;

return  0;


}