JZ16 --合併兩個排序鏈表（JS）

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題目描述：合併兩個排序鏈表

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輸入兩個單調遞增的鏈表，輸出兩個鏈表合成後的鏈表，當然我們需要合成後的鏈表滿足單調不減規則。

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題目解析：

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function Merge(pHead1, pHead2)
{
    // write code here
    let vHead = new ListNode(-1);
    let pre = vHead;
    
    while(pHead1 && pHead2){
        if(pHead1.val < pHead2.val){
            pre.next = pHead1;
            pHead1 = pHead1.next
        } else{
            pre.next = pHead2;
            pHead2 = pHead2.next
        }
        pre = pre.next;
    }
    
    //如果pHead1 爲空就將pHead2拼接在新鏈表後面，否則pHead1
    pre.next = pHead1 ? pHead1: pHead2;
    return vHead.next;
}

遞歸：

function Merge(pHead1, pHead2)
{
    // write code here
    let newHead=null;
    if(!pHead1) return pHead2;
    if(!pHead2) return pHead1;
    if(pHead1.val<pHead2.val){
        newHead = pHead1;
        newHead.next = Merge(pHead1.next,pHead2);
    }else{
        newHead=pHead2;
        newHead.next=Merge(pHead1,pHead2.next);
    }
    return newHead;
}