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  • Codeforces Round #394 (Div. 2) D. Dasha and Very Difficult Problem —— 贪心

    题目链接:http://codeforces.com/contest/761/problem/D



    D. Dasha and Very Difficult Problem
    time limit per test
    2 seconds
    memory limit per test
    256 megabytes
    input
    standard input
    output
    standard output

    Dasha logged into the system and began to solve problems. One of them is as follows:

    Given two sequences a and b of length n each you need to write a sequence c of length n, the i-th element of which is calculated as follows: ci = bi - ai.

    About sequences a and b we know that their elements are in the range from l to r. More formally, elements satisfy the following conditions: l ≤ ai ≤ r and l ≤ bi ≤ r. About sequence c we know that all its elements are distinct.

    Dasha wrote a solution to that problem quickly, but checking her work on the standard test was not so easy. Due to an error in the test system only the sequence a and the compressed sequence of the sequence c were known from that test.

    Let's give the definition to a compressed sequence. A compressed sequence of sequence c of length n is a sequence p of length n, so that pi equals to the number of integers which are less than or equal to ci in the sequence c. For example, for the sequence c = [250, 200, 300, 100, 50] the compressed sequence will be p = [4, 3, 5, 2, 1]. Pay attention that in c all integers are distinct. Consequently, the compressed sequence contains all integers from 1 to n inclusively.

    Help Dasha to find any sequence b for which the calculated compressed sequence of sequence c is correct.

    Input

    The first line contains three integers nlr (1 ≤ n ≤ 105, 1 ≤ l ≤ r ≤ 109) — the length of the sequence and boundaries of the segment where the elements of sequences a and b are.

    The next line contains n integers a1,  a2,  ...,  an (l ≤ ai ≤ r) — the elements of the sequence a.

    The next line contains n distinct integers p1,  p2,  ...,  pn (1 ≤ pi ≤ n) — the compressed sequence of the sequence c.

    Output

    If there is no the suitable sequence b, then in the only line print "-1".

    Otherwise, in the only line print n integers — the elements of any suitable sequence b.

    Examples
    input
    5 1 5
    1 1 1 1 1
    3 1 5 4 2
    
    output
    3 1 5 4 2 
    input
    4 2 9
    3 4 8 9
    3 2 1 4
    
    output
    2 2 2 9 
    input
    6 1 5
    1 1 1 1 1 1
    2 3 5 4 1 6
    
    output
    -1
    
    Note

    Sequence b which was found in the second sample is suitable, because calculated sequence c = [2 - 3, 2 - 4, 2 - 8, 9 - 9] = [ - 1,  - 2,  - 6, 0] (note that ci = bi - ai) has compressed sequence equals to p = [3, 2, 1, 4].



    题解:

    1.首先将a数组按照p数组排序,然后按照p数组从小到大开始推出b数组。由于p数组是递增的,所以每获得一个b[i],p可取的最小值就会增加。

    2.为了之后p的取值范围尽可能大,当前的p应该取范围内的最小值。

    3.p合适的最小值推导:

    假设当前p的最小值为minn, 则:minn<=p<=r-a。

    而因为b = p+a, l<=b<=r,所以:l-a<=p<=r-a。

    所以p合适的最小值 = max(minn, l-a)。



    代码如下:

    #include<bits/stdc++.h>
    using namespace std;
    typedef long long LL;
    const double eps = 1e-6;
    const int INF = 2e9;
    const LL LNF = 9e18;
    const int mod = 1e9+7;
    const int maxn = 1e5+10;
    
    int A[maxn], a[maxn], b[maxn], p[maxn];
    int n, l, r;
    
    void init()
    {
        scanf("%d%d%d",&n,&l,&r);
        for(int i = 1; i<=n; i++)
            scanf("%d",&A[i]);
        for(int i = 1; i<=n; i++)
        {
            scanf("%d",&p[i]);
            a[p[i]] = A[i];
        }
    }
    
    void solve()
    {
        int minn = -INF;
        for(int i = 1; i<=n; i++)
        {
            b[i] = max(minn, l-a[i])+a[i];  // b = p合适的最小值 + a
            minn = max(minn, l-a[i])+1; //p数组严格递增
            if(b[i]<l || b[i]>r)
            {
                puts("-1");
                return;
            }
        }
    
        for(int i = 1; i<=n; i++)
            printf("%d ",b[p[i]]);
    }
    
    int main()
    {
        init();
        solve();
    }
    


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  • 原文地址:https://www.cnblogs.com/DOLFAMINGO/p/7538652.html
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