第一种是高位在链表尾部
a = 7->1->2
b = 4->3
result = 1->5->2
没啥说的，注意进位，注意链表长度不一定一样
#include<stdio.h>
#include<stdlib.h>
/* Linked list node */
struct node
{
int data;
struct node* next;
};
/* Function to create a new node with given data */
struct node *newNode(int data)
{
struct node *new_node = (struct node *) malloc(sizeof(struct node));
new_node->data = data;
new_node->next = NULL;
return new_node;
}
/* Function to insert a node at the beginning of the Doubly Linked List */
void push(struct node** head_ref, int new_data)
{
/* allocate node */
struct node* new_node = newNode(new_data);
/* link the old list off the new node */
new_node->next = (*head_ref);
/* move the head to point to the new node */
(*head_ref) = new_node;
}
/* Adds contents of two linked lists and return the head node of resultant list */
struct node* addTwoLists (struct node* first, struct node* second)
{
struct node* res = NULL; // res is head node of the resultant list
struct node *temp, *prev = NULL;
int carry = 0, sum;
while (first != NULL || second != NULL) //while both lists exist
{
// Calculate value of next digit in resultant list.
// The next digit is sum of following things
// (i) Carry
// (ii) Next digit of first list (if there is a next digit)
// (ii) Next digit of second list (if there is a next digit)
sum = carry + (first? first->data: 0) + (second? second->data: 0);
// update carry for next calulation
carry = (sum >= 10)? 1 : 0;
// update sum if it is greater than 10
sum = sum % 10;
// Create a new node with sum as data
temp = newNode(sum);
// if this is the first node then set it as head of the resultant list
if(res == NULL)
res = temp;
else // If this is not the first node then connect it to the rest.
prev->next = temp;
// Set prev for next insertion
prev = temp;
// Move first and second pointers to next nodes
if (first) first = first->next;
if (second) second = second->next;
}
if (carry > 0)
temp->next = newNode(carry);
// return head of the resultant list
return res;
}
// A utility function to print a linked list
void printList(struct node *node)
{
while(node != NULL)
{
printf("%d ", node->data);
node = node->next;
}
printf("
");
}
/* Drier program to test above function */
int main(void)
{
struct node* res = NULL;
struct node* first = NULL;
struct node* second = NULL;
// create first list 7->5->9->4->6
push(&first, 6);
push(&first, 4);
push(&first, 9);
push(&first, 5);
push(&first, 7);
printf("First List is ");
printList(first);
// create second list 8->4
push(&second, 4);
push(&second, 8);
printf("Second List is ");
printList(second);
// Add the two lists and see result
res = addTwoLists(first, second);
printf("Resultant list is ");
printList(res);
return 0;
}
第二种是高位在链表头部
a = 2 -> 1 -> 7
b = 3 -> 4
result = 2 -> 5 -> 1
这个为了处理进位，需要用递归的思想
// A recursive program to add two linked lists
#include <stdio.h>
#include <stdlib.h>
// A linked List Node
struct node
{
int data;
struct node* next;
};
typedef struct node node;
/* A utility function to insert a node at the beginning of linked list */
void push(struct node** head_ref, int new_data)
{
/* allocate node */
struct node* new_node = (struct node*) malloc(sizeof(struct node));
/* put in the data */
new_node->data = new_data;
/* link the old list off the new node */
new_node->next = (*head_ref);
/* move the head to point to the new node */
(*head_ref) = new_node;
}
/* A utility function to print linked list */
void printList(struct node *node)
{
while (node != NULL)
{
printf("%d ", node->data);
node = node->next;
}
printf("
");
}
// A utility function to swap two pointers
void swapPointer( node** a, node** b )
{
node* t = *a;
*a = *b;
*b = t;
}
/* A utility function to get size of linked list */
int getSize(struct node *node)
{
int size = 0;
while (node != NULL)
{
node = node->next;
size++;
}
return size;
}
// Adds two linked lists of same size represented by head1 and head2 and returns
// head of the resultant linked list. Carry is propagated while returning from
// the recursion
node* addSameSize(node* head1, node* head2, int* carry)
{
// Since the function assumes linked lists are of same size,
// check any of the two head pointers
if (head1 == NULL)
return NULL;
int sum;
// Allocate memory for sum node of current two nodes
node* result = (node *)malloc(sizeof(node));
// Recursively add remaining nodes and get the carry
result->next = addSameSize(head1->next, head2->next, carry);
// add digits of current nodes and propagated carry
sum = head1->data + head2->data + *carry;
*carry = sum / 10;
sum = sum % 10;
// Assigne the sum to current node of resultant list
result->data = sum;
return result;
}
// This function is called after the smaller list is added to the bigger
// lists's sublist of same size. Once the right sublist is added, the carry
// must be added toe left side of larger list to get the final result.
void addCarryToRemaining(node* head1, node* cur, int* carry, node** result)
{
int sum;
// If diff. number of nodes are not traversed, add carry
if (head1 != cur)
{
addCarryToRemaining(head1->next, cur, carry, result);
sum = head1->data + *carry;
*carry = sum/10;
sum %= 10;
// add this node to the front of the result
push(result, sum);
}
}
// The main function that adds two linked lists represented by head1 and head2.
// The sum of two lists is stored in a list referred by result
void addList(node* head1, node* head2, node** result)
{
node *cur;
// first list is empty
if (head1 == NULL)
{
*result = head2;
return;
}
// second list is empty
else if (head2 == NULL)
{
*result = head1;
return;
}
int size1 = getSize(head1);
int size2 = getSize(head2) ;
int carry = 0;
// Add same size lists
if (size1 == size2)
*result = addSameSize(head1, head2, &carry);
else
{
int diff = abs(size1 - size2);
// First list should always be larger than second list.
// If not, swap pointers
if (size1 < size2)
swapPointer(&head1, &head2);
// move diff. number of nodes in first list
for (cur = head1; diff--; cur = cur->next);
// get addition of same size lists
*result = addSameSize(cur, head2, &carry);
// get addition of remaining first list and carry
addCarryToRemaining(head1, cur, &carry, result);
}
// if some carry is still there, add a new node to the fron of
// the result list. e.g. 999 and 87
if (carry)
push(result, carry);
}
// Driver program to test above functions
int main()
{
node *head1 = NULL, *head2 = NULL, *result = NULL;
int arr1[] = {9, 9, 9};
int arr2[] = {1, 8};
int size1 = sizeof(arr1) / sizeof(arr1[0]);
int size2 = sizeof(arr2) / sizeof(arr2[0]);
// Create first list as 9->9->9
int i;
for (i = size1-1; i >= 0; --i)
push(&head1, arr1[i]);
// Create second list as 1->8
for (i = size2-1; i >= 0; --i)
push(&head2, arr2[i]);
addList(head1, head2, &result);
printList(result);
getchar();
return 0;
}