P16175 F002B. Compressed vectors

#include <vector>
#include <iostream>

using namespace std;

struct Pair {
    int value;
    int pos;
};

typedef vector<Pair> Com_Vec;

Com_Vec sum(const Com_Vec& v1, const Com_Vec& v2){
    int a, b, s1 = v1.size(), s2 = v2.size();
    a = b = 0;
    Com_Vec v;
    while(a < s1 or b < s2){
        Pair p;
        if(a < s1 and b < s1){
            Pair p1 = v1[a], p2 = v2[b];
            if(p1.pos == p2.pos){
                p.pos = p1.pos;
                p.value = p1.value + p2.value;
                ++a;
                ++b;
            }
            else if(p1.pos < p2.pos){
                p.pos = p1.pos;
                p.value = p1.value;
                ++a;
            }
            else if(p2.pos < p1.pos){
                p.pos = p2.pos;
                p.value = p2.value;
                ++b;
            }
        }
        else if(a < s1){
            Pair p1 = v1[a];
            p.pos = p1.pos;
            p.value = p1.value;
            ++a;
        }
        else if(b < s2){
            Pair p2 = v2[b];
            p.pos = p2.pos;
            p.value = p2.value;
            ++b;
        }
        if(p.value != 0) v.push_back(p);
    }
    return v;
}

void p(const Com_Vec& v){
    int l = v.size();
    cout << l;
    for(int i = 0; i < l; ++i){
        cout << " " << v[i].value << ";" << v[i].pos;
    }
    cout << endl;
}

void read(Com_Vec& v){
    int n;
    cin >> n;
    Com_Vec cv(n);
    int i = 0;
    if(n == 0){
        Pair r;
        r.pos = 1;
        r.value = 0;
        cv.push_back(r);
    }
    while(n--){
        char c;
        cin >> cv[i].value >> c >> cv[i].pos;
        ++i;
    }

    v = cv;
}

int main() {
    int k;
    cin >> k;
    vector< Com_Vec> vc(2);
    while(k--){
        read(vc[0]);
        read(vc[1]);
        Com_Vec v = sum(vc[0], vc[1]);
        p(v);
    }
}