PAT 1009. Product of Polynomials (25)

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#include <stdio.h>#include <math.h>#include <string.h>#define  MAX 2000double arr1[MAX],arr2[MAX],result[2*MAX];int cnt=0,num1,num2;void read(double a[],int & num){    int id;    double tmp;    scanf("%d",&num);    for (int i=0; i<num; i++) {        scanf("%d%lf",&id,&tmp);        a[id]=tmp;    }}void product(){    for (int i=0; i<=1000; i++) {        for (int j=0; j<=1000; j++) {            result[i+j]+=arr1[i]*arr2[j];        }    }}void output(){    for (int i=0; i<=2000; i++) {        if (result[i]!=0) {            cnt++;        }    }    if (cnt!=0) {        printf("%d",cnt);        for (int i=2000; i>=0; i--) {//一定不要忘记了=0            if (result[i]) {                printf(" %d %.1f",i,result[i]);            }        }    }    puts("");}int main(){    freopen("/Users/pantingting/Documents/code/data/input", "r", stdin);    read(arr1,num1);    read(arr2,num2);    product();    output();    return 0;}

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