[436] LeetCode brush title

Coding everyday. ^_^

1. Two Sum

• Key knowledge: the pointer value can be stored by an array of new malloc
• int* returnSize：Size of the return array. Store the value in a pointer, say 2.
  *returnSize = 2
• My solution:

• /**
   * Note: The returned array must be malloced, assume caller calls free().
   */
  int* twoSum(int* nums, int numsSize, int target, int* returnSize){
      *returnSize = 2;
      int* returnArray = malloc(sizeof(int)*(*returnSize));
      for (int i = 0; i < numsSize-1; i++) {
          for (int j = i+1; j < numsSize; j++) {
              if (nums[i] + nums[j] == target) {
                  returnArray[0] = i;
                  returnArray[1] = j;
                  return returnArray;
              }
          }
      }
      returnArray[0] = -1;
      returnArray[1] = -1;
      return returnArray;
  }
  

   

2. Add Two Numbers

• Key knowledge: You can not be calculated by numbers, consider a carry, consider the list traversal and insertion node, the new node by malloc
• Don't use integer to calculate in this problem since the numbers are very long.
• Need to consider carry bit.
• This linked list's head is the first node.
• My solution:

• /**
   * Definition for singly-linked list.
   * struct ListNode {
   *     int val;
   *     struct ListNode *next;
   * };
   */
  
  
  struct ListNode* addTwoNumbers(struct ListNode* l1, struct ListNode* l2){
      struct ListNode* p1;
      struct ListNode* p2;
      struct ListNode* l3 = NULL;
      struct ListNode* p3 = NULL;
      p1 = l1;
      p2 = l2;
      
      int carry_bit = 0;
      while (p1 != NULL || p2 != NULL || carry_bit == 1) {
          int num1;
          int num2;
          int num3;
          if (p1 == NULL && p2 == NULL && carry_bit == 1) {
              num3 = 1;
              carry_bit = 0;
          }
          else {
              if (p1 == NULL) {
                  num1 = 0;
              }
              else {
                  num1 = p1->val;
                  p1 = p1->next;
              }
              if (p2 == NULL) {
                  num2 = 0;
              }
              else {
                  num2 = p2->val;
                  p2 = p2->next;
              }
              
              num3 = num1 + num2 + carry_bit;
              if (num3 >= 10) {
                  carry_bit = 1;
                  num3 = num3 - 10;
              }
              else {
                  carry_bit = 0;
              }
          }
  
          struct ListNode* tmp;
          tmp = malloc(sizeof(struct ListNode));
          if (tmp == NULL) {
              fprintf(stderr, "Out of memory.\n");
              exit(1);
          }
          tmp->val = num3;
          tmp->next = NULL;
          
          if (p3 == NULL) {
              p3 = tmp;
              l3 = p3;
          }
          else {
              p3->next = tmp;
              p3 = p3->next;
          }
      }
      
      return l3;
  }
  

 

3.