• Codeforces Round #633 (Div. 2) B. Sorted Adjacent Differences(排序)


    You have array of nn numbers a1,a2,,ana1,a2,…,an .

    Rearrange these numbers to satisfy |a1a2||a2a3||an1an||a1−a2|≤|a2−a3|≤…≤|an−1−an| , where |x||x| denotes absolute value of xx . It's always possible to find such rearrangement.

    Note that all numbers in aa are not necessarily different. In other words, some numbers of aa may be same.

    You have to answer independent tt test cases.

    Input

    The first line contains a single integer tt (1t1041≤t≤104 ) — the number of test cases.

    The first line of each test case contains single integer nn (3n1053≤n≤105 ) — the length of array aa . It is guaranteed that the sum of values of nn over all test cases in the input does not exceed 105105 .

    The second line of each test case contains nn integers a1,a2,,ana1,a2,…,an (109ai109−109≤ai≤109 ).

    Output

    For each test case, print the rearranged version of array aa which satisfies given condition. If there are multiple valid rearrangements, print any of them.

    Example
    Input
    Copy
    2
    6
    5 -2 4 8 6 5
    4
    8 1 4 2
    
    Output
    Copy
    5 5 4 6 8 -2
    1 2 4 8
    
    Note

    In the first test case, after given rearrangement, |a1a2|=0|a2a3|=1|a3a4|=2|a4a5|=2|a5a6|=10|a1−a2|=0≤|a2−a3|=1≤|a3−a4|=2≤|a4−a5|=2≤|a5−a6|=10 . There are other possible answers like "5 4 5 6 -2 8".

    In the second test case, after given rearrangement, |a1a2|=1|a2a3|=2|a3a4|=4|a1−a2|=1≤|a2−a3|=2≤|a3−a4|=4 . There are other possible answers like "2 4 8 1".

    大意就是排序后使得序列满足|a1a2||a2a3||a3a4||a4a5||a5a6|这样

    题目标题已经暗示的很明显了,sort后轮流把最后一个元素,第一个元素,倒数第二个元素,第二个元素...依次扔进vector,然后倒序输出即可。

    #include <bits/stdc++.h>
    using namespace std;
    int n;
    int a[100005];
    int main()
    {
        int t;
        cin>>t;
        while(t--)
        {
            int i,j;
            scanf("%d",&n);
            for(i=1;i<=n;i++)scanf("%d",&a[i]);
            sort(a+1,a+n+1);
            vector<int>v;
            i=1,j=n;
            while(i<=j)
            {
                v.push_back(a[j]);
                j--;
                if(i>j)break;
                v.push_back(a[i]);
                i++;
            }
            for(i=n-1;i>=0;i--)
            {
                printf("%d ",v[i]);
            }
            cout<<endl;
        }
        
    }
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  • 原文地址:https://www.cnblogs.com/lipoicyclic/p/12689923.html
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