唉，我太弱了，这么个简单的东西，还是用数组写的，却因为各种错误，弄了一个晚上，C++还得好好学啊，各种语法，要弄清楚。
1 #include <iostream>
2 #include <cstdlib>
3 #include <cstdio>
4 #include <iomanip>
5 #include <cstring>
6
7 using namespace std;
8
9 class Polynomial
10 {
11 public:
12 Polynomial(int = 0);
13 friend istream & operator >> (istream & input, Polynomial & pl);
14 friend ostream & operator << (ostream & output, Polynomial & pl);
15 Polynomial & operator += (Polynomial & add);
16 Polynomial & operator -= (Polynomial & add);
17 Polynomial & operator - (Polynomial & add);
18 Polynomial & operator * (Polynomial &);
19 Polynomial & operator + (Polynomial & add);
20 Polynomial & operator *= (Polynomial &);
21 Polynomial & operator = (Polynomial & right);
22 Polynomial & test(Polynomial & right);
23 private:
24 int *a;
25 int size, num;
26 };
27
28 Polynomial & Polynomial::operator *= (Polynomial & mu)
29 {
30 Polynomial b, c;
31 c = *this; b = *this;
32 for (int j=0,r=0; j<b.num;++j,r+=2)
33 {
34 (*this).a[r]+=mu.a[0]; (*this).a[r+1]*=mu.a[1];
35 }
36 for (int i=1,k=2;i<mu.num;++i,k+=2)
37 {
38 for (int j=0,r=0; j<b.num;++j,r+=2)
39 {
40 b.a[r]+=mu.a[k];
41 b.a[r+1]*=mu.a[k+1];
42 }
43 *this += b;
44 b = c;
45 }
46 return *this;
47 }
48 Polynomial & Polynomial::operator * (Polynomial & mu)
49 {
50 Polynomial b, c;
51 c = *this; b = *this;
52 for (int j=0,r=0; j<b.num;++j,r+=2)
53 {
54 (*this).a[r]+=mu.a[0]; (*this).a[r+1]*=mu.a[1];
55 }
56 for (int i=1,k=2;i<mu.num;++i,k+=2)
57 {
58 for (int j=0,r=0; j<b.num;++j,r+=2)
59 {
60 b.a[r]+=mu.a[k];
61 b.a[r+1]*=mu.a[k+1];
62 }
63 *this += b;
64 b = c;
65 }
66 return *this;
67 }
68
69 Polynomial & Polynomial::operator = (Polynomial & right)
70 {
71 if (&right != this)
72 {
73 delete [] a;
74 size = right.size;
75 num = right.num;
76 a = new int[size];
77 for (int i = 0; i < size; ++i)
78 a[i]=right.a[i];
79 }
80 else
81 cout<<"Attempted assignment of a polynomial to itself" << endl;
82 return *this;
83 }
84
85 Polynomial & Polynomial::operator -= (Polynomial & add)
86 {
87 int number = add.num, mrk = 0;
88 int cosize = add.size; int * q = new int[cosize];
89 for (int d=0;d<cosize;++d) q[d]=add.a[d];
90 for (int i = 0, s = 0; i < number; ++i, s+=2)
91 {
92 mrk = 0;
93 for (int j = 0, k = 0; j < num; ++j,k+=2)
94 {
95 if (q[s]==a[k])
96 {
97 mrk = 1;
98 a[k+1]-=q[s+1];
99 q[s+1]=0;
100 }
101 }
102 if (!mrk)
103 {
104 int *p = new int[size+2];
105 for (int d=0;d<size;d++)
106 p[d]=a[d];
107 p[size] = q[s];
108 p[size+1] = -q[s+1];
109 q[s+1]=0;
110 a = p;
111 num++;
112 size+=2;
113 }
114 }
115 return *this;
116 }
117 Polynomial & Polynomial::operator - (Polynomial & add)
118 {
119 int number = add.num, mrk = 0;
120 int cosize = add.size; int * q = new int[cosize];
121 for (int d=0;d<cosize;++d) q[d]=add.a[d];
122 for (int i = 0, s = 0; i < number; ++i, s+=2)
123 {
124 mrk = 0;
125 for (int j = 0, k = 0; j < num; ++j,k+=2)
126 {
127 if (q[s]==a[k])
128 {
129 mrk = 1;
130 a[k+1]-=q[s+1];
131 q[s+1]=0;
132 }
133 }
134 if (!mrk)
135 {
136 int *p = new int[size+2];
137 for (int d=0;d<size;d++)
138 p[d]=a[d];
139 p[size] = q[s];
140 p[size+1] = -q[s+1];
141 q[s+1]=0;
142 a = p;
143 num++;
144 size+=2;
145 }
146 }
147 return *this;
148 }
149
150 Polynomial & Polynomial::operator += (Polynomial & add)
151 {
152 int number = add.num, mrk = 0;
153 int cosize = add.size; int * q = new int[cosize];
154 for (int d=0;d<cosize;++d) q[d]=add.a[d];
155 for (int i = 0, s = 0; i < number; ++i, s+=2)
156 {
157 mrk = 0;
158 for (int j = 0, k = 0; j < num; ++j,k+=2)
159 {
160 if (q[s]==a[k])
161 {
162 mrk = 1;
163 a[k+1]+=q[s+1];
164 q[s+1]=0;
165 }
166 }
167 if (!mrk)
168 {
169 int *p = new int[size+2];
170 for (int d=0;d<size;d++)
171 p[d]=a[d];
172 p[size] = q[s];
173 p[size+1] = q[s+1];
174 q[s+1]=0;
175 a = p;
176 num++;
177 size+=2;
178 }
179 }
180 return *this;
181 }
182
183 Polynomial & Polynomial::operator + (Polynomial & add)
184 {
185 int number = add.num, mrk = 0;
186 Polynomial & mi = *this;
187 int cosize = add.size; int * q = new int[cosize];
188 for (int d=0;d<cosize;++d) q[d]=add.a[d];
189 for (int i = 0, s = 0; i < number; ++i, s+=2)
190 {
191 mrk = 0;
192 for (int j = 0, k = 0; j < mi.num; ++j,k+=2)
193 {
194 if (q[s]==mi.a[k])
195 {
196 mrk = 1;
197 mi.a[k+1]+=q[s+1];
198 q[s+1]=0;
199 }
200 }
201 if (!mrk)
202 {
203 int *p = new int[mi.size+2];
204 for (int d=0;d<mi.size;d++)
205 p[d]=mi.a[d];
206 p[mi.size] = q[s];
207 p[mi.size+1] = q[s+1];
208 q[s+1]=0;
209 mi.a = p;
210 mi.num++;
211 mi.size+=2;
212 }
213 }
214 return mi;
215 }
216
217 ostream & operator << (ostream & output, Polynomial & pl)
218 {
219 for (int i = 0, j = 0; i < pl.num; ++i)
220 {
221 if (pl.a[j+1]==0)
222 {
223 output << "0 0 "; j+=2; continue;
224 }
225 output << pl.a[j+1] << " " << pl.a[j] << " ";
226 j+=2;
227 }
228 output << endl;
229 return output;
230 }
231
232 istream & operator >> (istream & input, Polynomial & pl)
233 {
234 cout << "input the number of Polynomial terms: ";
235 input >> pl.num;
236 pl.size = pl.num * 2;
237 pl.a = new int[pl.size];
238 int s, t;
239 for (int i = 0, j = 0; i < pl.num;)
240 {
241 input >> s >> t;
242 pl.a[j] = t; pl.a[j+1] = s;
243 i++; j+=2;
244 }
245 return input;
246 }
247
248 Polynomial::Polynomial(int n)
249 :num(n)
250 {
251 size = num * 2;
252 a = new int[size];
253 }
254
255 int main(void)
256 {
257 Polynomial poly1, poly2, poly;
258 freopen("in", "r", stdin);
259
260 cin >> poly1;
261 cout << endl;
262 cin >> poly2;
263 cout << endl;
264
265 /* poly = poly1 + poly2;
266 cout << poly;
267
268 poly1 -= poly2;
269 poly = poly1;
270 cout << poly;
271 */
272 poly = poly1 * poly2;
273 cout << poly;
274
275 return 0;
276 }
这个程序写得不好，重载运算符+，-，和+=，-=，=的代码是一样的，以后再改一下。而且很多地方，效率很低，很繁琐。
总结一下：因为在一个成员函数里面重复定义了一个变量，导致怎么也不对。最后没办法，现学gdb调试了，唉，这才发现错误，以后写代码的时候要过脑子，别想怎么写就怎么写，想想为什么这么写，认真一点儿，就会节约很多时间！当程序出现错误的时候，你的信念不应该是：我的程序是对的啊，怎么看怎么对。而应该是这样的：我的程序肯定在某个地方出错了，然后一行一行地检查。这样才会尽快找出错误。
原文链接: https://www.cnblogs.com/liuxueyang/archive/2012/12/14/2817428.html
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