PAT甲级1002 A+B for Polynomials (25分)附测试点6段错误原因

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​N​1​​​​ N​2​​ a​N​2​​​​ ... N​K​​ a​N​K​​​​

where K is the number of nonzero terms in the polynomial, N​i​​ and a​N​i​​​​ (,) are the exponents and coefficients, respectively. It is given that 1，0.

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

 

 这个题可以用链表写，也可以用哈希表写，用哈希会更简单一些，不过最近在看严老师的数据结构，里面专门有再讲多项式的加减，于是用链表重新写了一遍。

测试点6要求输出0，也就是多项式每一项相加减抵消了。

附代码：

#include <iostream>
using namespace std;
struct Node{
    int expn;//表示指数
    double coef;//表示系数
    Node*next;
};
void InitList(Node*L,int n){
    for(int i=0;i<n;i++){
        Node*a=(Node*)malloc(sizeof(Node));
        cin>>a->expn>>a->coef;
        L->next=a;
        L=a;
    } 
    L->next=NULL;
}
int main() {
    Node*La=(Node*)malloc(sizeof(Node));
    Node*Lb=(Node*)malloc(sizeof(Node));
    //La和Lb分表代表着两个链表      
    int n;
    cin>>n;
    InitList(La,n);
    cin>>n;
    InitList(Lb,n); 
    Node*pa=La->next,*pb=Lb->next;//工作指针
    Node*Lc=La,*pc=Lc;//用La的头结点作为Lc的头结点 
    while(pa&&pb){
        if(pa->expn>pb->expn){
            pc->next=pa;
            pc=pa;
            pa=pa->next;
        }
        else if(pa->expn<pb->expn){
            pc->next=pb;
            pc=pb;
            pb=pb->next;
        }
        else if(pa->expn==pb->expn){
            pa->coef+=pb->coef;
            if(pa->coef!=0.0){
                pc->next=pa;
                pc=pa;
            }
            pa=pa->next;
            pb=pb->next;
        }
    }
    if(pa)
        pc->next=pa;
    else
    {
        pc->next=pb;
    }
    pc=Lc;
    int len=0;
    while(pc->next!=NULL){
        len++;
        pc=pc->next;
    }
    cout<<len;
    pc=Lc->next;
    while(pc!=NULL){
        printf(" %d %.1f",pc->expn,pc->coef);
        pc=pc->next;
    }
    return 0;
}