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Linked List addition in C++
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#include <string> | |
class List { | |
struct Node { | |
Node* next; | |
int val; | |
Node(int val, Node* next = nullptr) | |
: next(next), val(val) {} | |
}; | |
Node* head_; | |
explicit List(Node* head) : head_(head) {} | |
public: | |
List() : head_(nullptr) {} | |
~List() { | |
while (head_) { | |
Node* next = head_->next; | |
delete head_; | |
head_ = next; | |
} | |
} | |
explicit List(const char* n) : head_(nullptr) { | |
for (; *n != '\0'; ++n) { | |
assert(*n >= '0' && *n <= '9'); | |
push(*n - '0'); | |
} | |
} | |
List& push(int n) { | |
head_ = new Node(n, head_); | |
return *this; | |
} | |
std::string to_string() const { | |
std::string r; | |
for (Node* p = head_; p; p = p->next) | |
r += static_cast<char>(p->val + '0'); | |
std::reverse(r.begin(), r.end()); | |
return r; | |
} | |
List operator+(List const& b) const { | |
Node *prev = nullptr, *l = head_, *r = b.head_; | |
List ret; | |
int carry = 0; | |
for (; l && r; l = l->next, r = r->next) | |
ret.append_carry(prev, carry += l->val + r->val); | |
for (; l; l = l->next) | |
ret.append_carry(prev, carry += l->val); | |
for (; r; r = r->next) | |
ret.append_carry(prev, carry += r->val); | |
while (carry) | |
ret.append_carry(prev, carry); | |
return ret; | |
} | |
private: | |
const static int RADIX = 10; | |
void append_carry(Node*& prev, int& carry) { | |
Node* n = new Node(carry % RADIX); | |
carry /= RADIX; | |
if (prev != nullptr) prev->next = n; | |
if (head_ == nullptr) head_ = prev; | |
prev = n; | |
} | |
}; | |
#include <iostream> | |
int main(void) | |
{ | |
std::cout << (List("123") + List("456")).to_string() << std::endl; | |
std::cout << (List("123000") + List("456")).to_string() << std::endl; | |
std::cout << (List("123") + List("456000")).to_string() << std::endl; | |
return 0; | |
} |
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