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function tree(array) {
    let treeNodes = new Map()
    let rootNode
    array.forEach((item) => {
        if (!treeNodes.has(item.c)) {
            let newNode = {
                val: item.c,
                children: []
            }
            treeNodes.set(item.c,newNode)
        }
        let childNode = treeNodes.get(item.c)
        if (!treeNodes.has(item.p)) {
            let newNode = {
                val: item.p,
                children: []
            }
            treeNodes.set(item.p,newNode)
        }
        let parentNode = treeNodes.get(item.p)
        parentNode.children.push(childNode)
    })
     
    for (let i=0; i<array.length; i++) {
      let flag = true
      for (let j=0; j<array.length; j++) {
        if (array[i].p === array[j].c) {
          flag = false
        }
      }
      if (flag) {
        rootNode = array[i].p
      }
    }
    
    return treeNodes.get(rootNode)
}
function removeDuplicate(head) {
    var curNode = head
    while(curNode) {
        var nextNode = curNode.next
        while(nextNode) {
            if(curNode.value === nextNode.value) {
                var preNode = nextNode.pre
                var nextNodeNext = nextNode.next
                preNode.next = nextNodeNext
                nextNodeNext.pre = preNode
            } else {
                nextNode = nextNode.next
            }
        }
        curNode = curNode.next
    }
}
function sizeof(obj) {
    let num = 0
    for(let key in obj){
        if (!obj[key] || typeof obj[key] !== 'object') {
            num = 
        }
        num = num + sizeof(obj[key])
    }
    return num
}