BigInteger in Cpp (造轮子大法第一波) 未完成版本

  1 bool BigInt::equal(const BigInt &bi) const {
  2     if (this->num.size() != bi.num.size())
  3         return false;
  4     for (decltype(bi.num.size()) i = 0; i < bi.num.size(); i++) {
  5         if (this->num[i] != bi.num[i])
  6             return false;
  7     }
  8     return true;
  9 }
 10 BigInt BigInt::operator+(const BigInt &bi) {
 11     if (this->positive == bi.positive) {
 12         //存在拷贝构造 性能问题??
 13         BigInt ans = add(bi);
 14         ans.setPositive(bi.positive);
 15         return ans;
 16     }
 17     else {
 18         BigInt ans;
 19         if (this->less(bi)) {
 20             ans = bi.minus(*this);
 21             ans.setPositive(bi.positive);
 22         }
 23         else if (this->equal(bi)) {
 24             ans.num.push_back(0);
 25             return ans;
 26         }
 27         else {
 28             ans = this->minus(bi);
 29             ans.setPositive(this->positive);
 30         }
 31         return ans;
 32     }
 33     
 34 }
 35 BigInt BigInt::operator-(const BigInt &bi) {
 36     if (this->positive == bi.positive) {
 37         BigInt ans;
 38         if (this->less(bi)) {
 39             ans = bi.minus(*this);
 40             ans.setPositive(!this->positive);
 41         }
 42         else if (this->equal(bi)) {
 43             ans.num.push_back(0);
 44         }
 45         else {
 46             ans = this->minus(bi);
 47             ans.setPositive(this->positive);
 48         }
 49         return ans;
 50     }
 51     else {
 52         BigInt ans = this->add(bi);
 53         ans.setPositive(this->positive);
 54         return ans;
 55     }
 56 }
 57 BigInt BigInt::operator*(const BigInt &bi) {
 58     if (*this == *(new BigInt(0)) || bi == *(new BigInt(0))) {
 59         BigInt ans;
 60         ans.num.push_back(0);
 61         return ans;
 62     }
 63     else {
 64         int t = 0;
 65         // 使用隐式转换 安全?
 66         BigInt ans = 0;
 67         for (decltype(num.size()) i = 0; i < num.size(); i++) {
 68             ans = ans + bi.multiply(i, t);
 69             t++;
 70         }
 71         if (this->positive != bi.positive) {
 72             ans.setPositive(false);
 73         }
 74         return ans;
 75     }
 76 }
 77 void BigInt::setPositive(bool flag) {
 78     this->positive = flag;
 79 }
 80 bool BigInt::operator==(const BigInt &bi) const {
 81     if (this->positive != bi.positive)
 82         return false;
 83     else {
 84         if (this->num.size() != bi.num.size())
 85             return false;
 86         for (decltype(bi.num.size()) i = 0; i < bi.num.size(); i++) {
 87             if (this->num[i] != bi.num[i])
 88                 return false;
 89         }
 90         return true;
 91     }
 92 }
 93 bool BigInt::operator<(const BigInt &bi) const {
 94     if (this->positive == true) {  
 95         if (bi.positive == false)    //this为正 bi为负
 96             return false;
 97         else {    //this与bi同为正
 98             if (this->num.size() > bi.num.size())   //长度长的大
 99                 return false;
100             else if (this->num.size() < bi.num.size())
101                 return true;
102             bool flag = false;
103             //一样长的时候比较为一位 注意要逆序比较 以为数字的首位存在容器的最后一位
104             for (int i = this->num.size() - 1; i >= 0; i--) {
105                     if (this->num[i] > bi.num[i]) {
106                         flag = true;
107                         break;
108                     }
109             }
110             return flag;
111 
112         }
113     }
114     else {   // 跟以上反过来就行了
115         if (bi.positive == true)  //this为负 bi为正
116             return true;
117         else { //同为负数时
118             if (this->num.size() > bi.num.size())
119                 return true;
120             else if (this->num.size() < bi.num.size())
121                 return false;;
122             bool flag = false;
123             for (int i = this->num.size() - 1; i >= 0; i--) {
124                     if (this->num[i] < bi.num[i]) {
125                         flag = true;
126                         break;
127                     }
128             }
129             return !flag;
130         }
131     }
132         
133 }
134 bool BigInt::operator>(const BigInt &bi) const {
135     if (*this < bi)
136         return false;
137     else if (*this == bi)
138         return false;
139     else
140         return true;
141 }
142 istream& operator>>(istream &in, BigInt &bi) {
143     string input;            //读取所创建的大数
144     in >> input;
145     while (!bi.num.empty())
146         bi.num.clear();
147     try {
148         if (input[0] == ‘-‘)
149             bi.positive = false;
150         else
151             bi.positive = true;
152         for (int i = input.size() - 1; i >= 0; i--) {
153             if (0 == i && !bi.positive)
154                 break;
155             if (input[i] < ‘0‘ || input[i] > ‘9‘)
156                 throw runtime_error("You should input a positive integer.");
157             bi.num.push_back(input[i] - ‘0‘);
158         }
159     }
160     catch (runtime_error e) {
161         std::cerr << e.what() << endl;
162     }
163     return in;
164 }
165 ostream& operator<<(ostream &os, const BigInt &bi) {
166     // 逆序输出
167     if (!bi.positive)
168         os << "-";
169     for (int i = bi.num.size() - 1; i >= 0; i--) {
170         os << bi.num[i];
171     }
172     return os;
173 }