###### tags: `LeetCode` `C` `Two Sum`
# LeetCode

1 Two Sum
===

int* twoSum(int* nums, int numsSize, int target, int* returnSize){
    int i, j;
    int  *ptr;
    *returnSize=2;
   for(i=0;i<numsSize;i++){
       for (j=i;j<numsSize-1;j++){
            if (nums[i]+nums[j+1]==target){
                ptr=(int*)malloc(2*sizeof(int));
                *(ptr)=i;
                *(ptr+1)=j+1;
                                          
            }                   
       }      
}
    return ptr;  
   // return NULL; 
}

來源: [Leetcode 1. Two Sum](https://leetcode.com/problems/two-sum/)

21 Merge Two Sorted Lists
===

struct ListNode mergeTwoLists(struct ListNode l1, struct ListNode* l2){
struct ListNode* newnode=(struct ListNode*)malloc(sizeof(struct ListNode));
struct ListNode* new=newnode;
if(l1==NULL)return l2;
if(l2==NULL)return l1;
while(l1!=NULL && l2!=NULL)
{
    if(l1->val <= l2->val) 
    {
        new->next=l1;
        
        l1=l1->next; 
    }
    else 
    {
        new->next=l2;
        
        l2=l2->next;
        
    }
    
    new=new->next;  
    
}
    
if(l1==NULL) new->next=l2;
      
else if(l2==NULL)new->next=l1;
       
return newnode->next;}

206 Reverse Linked List
===

struct ListNode* reverseList(struct ListNode* head){
    
    struct ListNode *cur=head, *pre=NULL, *next;
  
    while(cur!=NULL){
        next=cur->next;
        cur->next=pre;
        pre=cur;
        cur=next;
        
    }
    
return pre;
}

來源: [206. Reverse Linked List](https://leetcode.com/problems/reverse-linked-list/)

136 Single Number
===

int singleNumber(int* nums, int numsSize){


   int result = 0;
    for (int i = 0; i<numsSize; i++)
    {
		result ^=nums[i];
    }
	return result;
    }

來源: [136. Single Number](https://leetcode.com/problems/single-number/)

190 Reverse Bits
===

uint32_t reverseBits(uint32_t n) {
    uint32_t b={0};   
    for(int i=0;i<32;i++){
          b<<=1;
        b+=n&1;
      n>>=1;
    }
   return b;    
}

來源: [190. Reverse Bits](https://leetcode.com/problems/reverse-bits/)

191 Number of 1 Bits
===

int hammingWeight(uint32_t n) {
    
    int count=0;
    while(n!=0){
   if(n&1) 
    
    count++;
    
   n>>=1;
   }
    return count;
}

來源: [191. Number of 1 Bits](https://leetcode.com/problems/number-of-1-bits/)

344 Reverse String
===

void reverseString(char* s, int sSize){
int i;
char temp;   
    
    for(int i=0;i<=(sSize-1)/2;i++){
    temp=s[i];
    s[i]=s[sSize-1-i];
    s[sSize-1-i]=temp;
          
      
    }
    
    return s;
    
}

來源: [344. Reverse String](https://leetcode.com/problems/reverse-string/)

617 Merge Two Binary Trees
===

struct TreeNode* mergeTrees(struct TreeNode* root1, struct TreeNode* root2){

    if (root1 == NULL)
        return root2;
    else if (root2 == NULL)
        return root1;
    root1->val += root2->val;
    root1->left = mergeTrees(root1->left, root2->left);
    root1->right = mergeTrees(root1->right, root2->right);
    return root1;
    
    
    
}

來源: [617. Merge Two Binary Trees](https://leetcode.com/problems/merge-two-binary-trees/)

1486 XOR Operation in an Array
===

int xorOperation(int n, int start){
    int result=0;
    int nums[n];
  for (int i=0;i<n;i++){
      nums[i] =start + 2*i;
      result^=nums[i];
  }
    
    return result;    
}

來源: [1486. XOR Operation in an Array](https://leetcode.com/problems/xor-operation-in-an-array/)