PAT (Advanced Level) Practise —— 1002. A+B for Polynomials

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http://pat.zju.edu.cn/contests/pat-a-practise/1002

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 3.22 2 1.5 1 0.5

Sample Output

3 2 1.5 1 2.9 0 3.2

说明：利用hash表思想，开辟数组，数组的下标作为多项式的指数，对应下标的数组元素为相应系数。

PS: WA了三次，总结一下：

1. 浮点数非零的判断

//判断对应的二次项是否为0if(fabs(coef[i] > 1e-10)){++m;}

2. scanf函数的使用：scanf("%.f", &flt)是错误的；scanf一次读入多个数据的时候格式控制字符中间可以无空格，如scanf("%d lf", &a, &b);可改为scanf("%d%lf", &a, &b);

我的代码：

#include <stdio.h>float poly1[1000+5] = {0.0f};float poly2[1000+5] = {0.0f};float re[1000+5] = {0.0f};int main(){int K1, K2;int i, expo = 0;float coeff = 0.0f;int itemNum = 0;scanf("%d", &K1);for (i = 0; i < K1; i++){scanf("%d%f", &expo, &coeff);poly1[expo] = coeff;}scanf("%d", &K2);for (i = 0; i < K2; i++){scanf("%d%f", &expo, &coeff);poly2[expo] = coeff;}for (i = 0; i <= 1000; i++){re[i] = poly1[i] + poly2[i];if (re[i]){itemNum++;}}printf("%d", itemNum);for (i = 1000; i >= 0; i--){if (re[i]){printf(" %d %.1f", i, re[i]);}}printf("\n");return 0;}

九度社区给出的答案：(只用一个数组即可！)

#include <cstdio>#include <cmath>const int MAXN = 1024;double coef[MAXN];int main(){for (int i= 0; i < 2; i++){int n;//输入第1个多项式非零项的系数scanf("%d", &n);while (n--){int a;double b;//输入该非零项对应的指数和系数scanf("%d%lf", &a, &b);coef[a] += b;}}int m = 0;for (int i = 0; i < MAXN; i++){//判断对应的二次项是否为0if(fabs(coef[i] > 1e-10)){++m;}}printf("%d", m);for (int i = MAXN-1; i >= 0; --i){//输出非零的二次项的次数和系数if(fabs(coef[i] > 1e-10)){printf(" %d %.1lf", i, coef[i]);}}puts("");return 0;}