【JAVA】1002 A+B for Polynomials (25分) PAT甲级 PAT (Advanced Level) Practice

1002 A+B for Polynomials (25分)

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 $N_1$ $a_N1$ $N_2$ $a_N2$… $N_K$ $a_NK$
每个输入文件包含一个测试用例。 每个案例占用2行，并且每行包含一个多项式的信息：
K $N_1$ $a_N1$ $N_2$ $a_N2$… $N_K$ $a_NK$

where K is the number of nonzero terms in the polynomial, $N_i$and$a_Ni$(i=1,2,⋯,K) are the exponents and coefficients, respectively. It is given that 1≤K≤10，0≤$N_K$​<⋯<$N_2$<$N_1$≤1000.
其中K是多项式中非零项的数量，$N_i$and$a_Ni$(i=1,2,⋯,K) 分别是指数和系数。 假设1≤K≤10，0≤$N_K$​<⋯<$N_2$<$N_1$≤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.
对于每个测试用例，应在一行中输出A和B的总和，格式与输入相同。 请注意，每行末尾不得有多余的空间。 请精确到小数点后一位。

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

要点

1. 最难理解的是题目
   

2. 请注意，每行末尾不得有多余的空间。

3. 请精确到小数点后一位。

   System.out.printf("%.1f", C[i]);
   

4. 注意一个特殊样例，比如输入两行分别是
   1 2 1
   1 2 -1
   这就是$x^2$+$-x^2$,输出为0

代码

import java.util.Arrays;
import java.util.Scanner;

public class PolynomialAddition1 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        Double[] A = new Double[1001];
        for (int i = 0; i < 1001; i++) { //防止 C[i] = A[i] + B[i];发生空指针异常
            A[i] = 0.0;
        }
        Double[] B = new Double[1001];
        for (int i = 0; i < 1001; i++) {//防止 C[i] = A[i] + B[i];发生空指针异常
            B[i] = 0.0;
        }

        int K = sc.nextInt();
        int index;
        while (K != 0) {
            index = sc.nextInt(); //指数
            A[index] = sc.nextDouble(); //系数
            K--;
        }
//        System.out.println(Arrays.toString(A));

        K = sc.nextInt();
        while (K != 0) {
            index = sc.nextInt(); //指数
            B[index] = sc.nextDouble(); //系数
            K--;
        }
        sc.close();
//        System.out.println(Arrays.toString(B));

        double[] C = new double[1001];
        int count = 0;
        /*//错误
        for (int i = 0; i < 1001; i++) {
            if (A[i] != 0 || B[i] != 0) {
            //这得小心一种情况。输入的两行分别是 a:1 1 1  b:1 1 -1。
            //A[1]+B[1]=0,这时count不应该再加
                count++;
                C[i] = A[i] + B[i];
            }
        }*/
        //改正
        for (int i = 0; i < 1001; i++) {
            C[i] = A[i] + B[i];
            if ((A[i] != 0 || B[i] != 0) && C[i] != 0) {
                // 这得小心一种情况。输入的两行分别是 a:1 1 1  b:1 1 -1。
                // A[1]+B[1]=0,这时count不应该再加
                count++;
            }
        }
//        System.out.println(Arrays.toString(C));
        System.out.print(count);
        for (int i = 1000; i >= 0; i--) {
            if (C[i] != 0) {
                System.out.print(" " + i + " ");
                System.out.printf("%.1f", C[i]);
            }
        }
    }
}