leetcode two sum solution c++ code example

Example 1: two sum problem in c++

bool twosum(int A[], int N, int X) {
  	sort(A, A+N);
    int i = 0, j = N-1;
    while (i < j) {
        if (A[i] + A[j] == X) return true;
        else if (A[i] + A[j] > X) j--;
        else i++;
    }
    return false;
}

Example 2: Leetcode two number sum

/*
2 -> 4 -> 3
5 -> 6 -> 4
7    0    8
*/
public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
    ListNode fake = new ListNode(0);
    ListNode p = fake;
 
    ListNode p1 = l1;
    ListNode p2 = l2;
 
    int carry = 0;
    while(p1!=null || p2!=null){
        int sum = carry;
        if(p1!=null){
            sum += p1.val;
            p1 = p1.next;
        }
 
        if(p2!=null){
            sum += p2.val;
            p2 = p2.next;
        }
 
        if(sum>9){
            carry=1;
            sum = sum-10;
        }else{
            carry = 0;
        }
 
        ListNode l = new ListNode(sum);
        p.next = l;
        p = p.next;
    }
 
    //don't forget check the carry value at the end
    if(carry > 0){
        ListNode l = new ListNode(carry);
        p.next = l;
    }
    return fake.next;
}