day02

合并两个有序链表

链表的特点：
无法直接获取第几个数/最后一个数
唯一的操作 .next

var mergeTwoLists = function(list1, list2) {
    let curr = new ListNode();
    let dummy = curr;//占住头部

    // 进行比较
    while( list1 !== null && list2 !== null){
        if(list1.val < list2.val ){
            curr.next = list1;
            list1 = list1.next;
        }else{
            curr.next = list2;
            list2 = list2.next;
        }
        curr = curr.next;//移动指针      
    }
    if(list1 !== null){
        curr.next = list1;
    }
    if(list2 !== null){
        curr.next = list2;
    }
    return dummy.next;
};

两两交换链表中的结果

大数相加

var addStrings = function(num1, num2) {
    const numArr1 = num1.split('').reverse();
    const numArr2 = num2.split('').reverse();
    let temp = 0;
    let index = 0;
    const result = [];
    while(numArr1.length > index || numArr2.length > index){
        let item1 = numArr1.length > index ? numArr1[index] : 0;
        let item2 = numArr2.length > index ? numArr2[index] : 0;
        let res = Number(item1) + Number(item2) + temp;
        temp = res > 9 ? 1: 0;
        result.push(res % 10);
        index++;
    }
    if(temp === 1){ result.push(1) }
    return result.reverse().join('');
};