PTA-Advance-1002

PROBLEM

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

#### Input Specification:

Each input file contains one test case. Each case occupies 2 lines, and each line contains the information of a polynomial:

K N1 aN1 N2 aN2 … NK aNK

where K is the number of nonzero terms in the polynomial, Ni and aNi (i=1,2,⋯,K) are the exponents and coefficients, respectively. It is given that 1≤K≤10，0≤NK<⋯<N2<N1≤1000.

Output Specification:

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

ACCEPTED CODE

#include <iostream>
#include <map>
using namespace std;
int main () {
	map<int , double, greater<int>> m;
	int k, count = 0;
	cin >> k;
	for (int i = 0; i < k; i++) {
		double exp , cof;
		cin >> exp >> cof;
		m[exp] += cof;
	}
	cin >> k;
	for (int i = 0; i < k; i++) {
		double exp , cof;
		cin >> exp >> cof;
		m[exp] += cof;
		if (m[exp] == 0) count++;//if this item is zero, count++
	}
	printf ("%d", m.size() - count);//print the nonzero item num, if result is zero, print zero
	for (map<int, double>::iterator ite = m.begin(); ite != m.end(); ite++) {
		if (ite->second != 0)//if this item is zero, do not print
			printf (" %d %.1lf", ite->first, ite->second);
	}
	return 0;
}

THINKING AND NOTICES

1. Creating a map from the exponents to coefficients. Add up the two coefficients of each exponents.

2. Print a zero(the total number of nonzero items) if the result of a+b is zero.

3. Map will sort your data by the keys in declining order, but you should print it in increasing order, so give map the third parameter – the class or struct name which has a member function like this:bool operator() (const double& str1, const double& str2);, a function (I’m not sure.) greater<int> ,or you can simply traversal the map from the end of it.

REFLECTION AND COMMENT

• Noting to reflect.