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  • codeforces 660C C. Hard Process(二分)

    题目链接:

    C. Hard Process

    time limit per test
    1 second
    memory limit per test
    256 megabytes
    input
    standard input
    output
    standard output

    You are given an array a with n elements. Each element of a is either 0 or 1.

    Let's denote the length of the longest subsegment of consecutive elements in a, consisting of only numbers one, as f(a). You can change no more than k zeroes to ones to maximize f(a).

    Input

    The first line contains two integers n and k (1 ≤ n ≤ 3·105, 0 ≤ k ≤ n) — the number of elements in a and the parameter k.

    The second line contains n integers ai (0 ≤ ai ≤ 1) — the elements of a.

    Output

    On the first line print a non-negative integer z — the maximal value of f(a) after no more than k changes of zeroes to ones.

    On the second line print n integers aj — the elements of the array a after the changes.

    If there are multiple answers, you can print any one of them.

    Examples
    input
    7 1
    1 0 0 1 1 0 1
    output
    4
    1 0 0 1 1 1 1
    input
    10 2
    1 0 0 1 0 1 0 1 0 1
    output
    5
    1 0 0 1 1 1 1 1 0 1


    题意:

    最多把k个0变成1,变完后连续的最长的全是1的串的长度是多少,并且输出最后得串;


    思路:


    用一个数组记录当前位一共有多少个0,暴力枚举最长串的最后一位,二分查找最长串的第一个1的位置;更新结果并记录好最长串的开始和结束位置,最后再输出就好啦;

    AC代码:
    /*
    2014300227    660C - 5    GNU C++11    Accepted    93 ms    4388 KB
    */
    #include <bits/stdc++.h>
    using namespace std;
    const int N=3e5+4;
    typedef long long ll;
    const double PI=acos(-1.0);
    int n,a[N],k,b[N];
    int check(int x,int y)
    {
        if(b[y]-b[x-1]<=k)return 1;
        return 0;
    }
    int bis(int num)
    {
        int l=1,r=num,mid;
        while(l<=r)
        {
            mid=(l+r)>>1;
            if(check(mid,num))r=mid-1;
            else l=mid+1;
        }
        return r+1;
    }
    int main()
    {
        scanf("%d%d",&n,&k);
        for(int i=1;i<=n;i++)
        {
            scanf("%d",&a[i]);
            if(!a[i])b[i]=b[i-1]+1;
            else b[i]=b[i-1];
        }
        int ans=0,l=0,r=0;
        for(int i=1;i<=n;i++)
        {
            int fx=bis(i);
            if(i-fx+1>ans)
            {
                ans=i-fx+1;
                l=fx;
                r=i;
            }
        }
        printf("%d
    ",ans);
        for(int i=1;i<=n;i++)
        {
            if(i>=l&&i<=r)
            {
                printf("1 ");
            }
            else printf("%d ",a[i]);
        }
        return 0;
    }


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  • 原文地址:https://www.cnblogs.com/zhangchengc919/p/5370488.html
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