2-add-two-numbers.js

/**
 * Definition for singly-linked list.
 * function ListNode(val, next) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.next = (next===undefined ? null : next)
 * }
 */
/**
 * @param {ListNode} l1
 * @param {ListNode} l2
 * @return {ListNode}
 */
const addTwoNumbers = function(l1, l2) {
  let res = new ListNode(null)
  let inc = false
  let cur = res
  while(l1 || l2 || inc) {
    const tmp = ((l1 && l1.val) || 0) + ((l2 && l2.val) || 0) + (inc ? 1 : 0)
    if(tmp >= 10) inc = true
    else inc = false
    cur.next = new ListNode(tmp % 10)
    cur = cur.next
    if(l1) l1 = l1.next
    if(l2) l2 = l2.next
  }
  
  return res.next
};

// another

/**
 * Definition for singly-linked list.
 * function ListNode(val) {
 *     this.val = val;
 *     this.next = null;
 * }
 */
/**
 * @param {ListNode} l1
 * @param {ListNode} l2
 * @return {ListNode}
 */
const addTwoNumbers = function(l1, l2) {
  const res = new ListNode(null);
  single(l1, l2, res);
  return res.next;
};

function single(l1, l2, res) {
  let cur;
  let addOne = 0;
  let sum = 0;
  let curVal = 0;
  while (l1 || l2 || addOne) {
    sum = ((l1 && l1.val) || 0) + ((l2 && l2.val) || 0) + addOne;
    if (sum / 10 >= 1) {
      curVal = sum % 10;
      addOne = 1;
    } else {
      curVal = sum;
      addOne = 0;
    }

    if (cur) {
      cur = cur.next = new ListNode(curVal);
    } else {
      cur = res.next = new ListNode(curVal);
    }

    if (l1) {
      l1 = l1.next;
    }
    if (l2) {
      l2 = l2.next;
    }
  }
}

// another

/**
 * Definition for singly-linked list.
 * function ListNode(val, next) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.next = (next===undefined ? null : next)
 * }
 */
/**
 * @param {ListNode} l1
 * @param {ListNode} l2
 * @return {ListNode}
 */
const addTwoNumbers = function(l1, l2) {
  let extra = false
  const dummy = new ListNode()
  let cur = dummy
  while(l1 || l2) {
    let val = 0
    if(l1) val += l1.val
    if(l2) val += l2.val
    if(extra) val += 1
      
    if(val > 9) {
      extra = true
      val = val % 10
    } else {
      extra = false
    }
    cur.next = new ListNode(val)
    cur = cur.next
    if(l1) l1 = l1.next
    if(l2) l2 = l2.next
  }

  if(extra) cur.next = new ListNode(1)
  return dummy.next
};

// another

/**
 * Definition for singly-linked list.
 * function ListNode(val, next) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.next = (next===undefined ? null : next)
 * }
 */
/**
 * @param {ListNode} l1
 * @param {ListNode} l2
 * @return {ListNode}
 */
const addTwoNumbers = function(l1, l2) {
  const dummy = new ListNode(null)
  let cur = dummy, carry = 0
  
  while(l1 || l2) {
    let v = 0
    if(l1 && l2) {
      v = l1.val + l2.val + carry
      l1 = l1.next
      l2 = l2.next
    } else {
      const node = l1 || l2
      v = node.val + carry
      if(l1) l1 = l1.next
      if(l2) l2 = l2.next
    }
    
    cur.next = new ListNode(v % 10)
    cur = cur.next
    if(v >= 10) carry = 1
    else carry = 0
  }
  
  if(carry) cur.next = new ListNode(1)
  
  return dummy.next
};