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Input: head = [1,2,3,4,5], k = 2
Output: [1,4,3,2,5]


Input: head = [7,9,6,6,7,8,3,0,9,5], k = 5
Output: [7,9,6,6,8,7,3,0,9,5]


var swapNodes = function(head, k) {
    let current = head;
    let p1 = k - 1;
    let p2 = 0;
    const arr = [];
    
    while(current !== null){
        arr.push(current);
        current = current.next;
    }
    
    p2 = arr.length - k;
    
    [arr[p1].val, arr[p2].val] = [arr[p2].val, arr[p1].val];
    
    return head;
};


// 642 ms, faster than 30.31%
var swapNodes = function(head, k) {
    const res = head;
    
    const nodes = {};
    let idx = 0;
    
    let now = head;
    while (now) {
        idx += 1;
        nodes[idx] = now;
        now = now.next;
    }
    
    const target = idx - k + 1;
    
    [nodes[k].val, nodes[target].val] = [nodes[target].val, nodes[k].val]
    
    return res;
};

Swapping Nodes in a Linked List

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