平常水题 - CodeForces - 660C(二分)
2017-03-29 21:05
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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.
Example
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:有n个数(0 或 1)序列,可以执行最多k次操作把 0 改为 1 ,问在满足条件的情况下连续为 1 的序列最大的长度。
解题思路:用二分法。ans[i]记录当前 i 位置之前(包括当前位置),有多少个 1 。
x :从 i 位置开始(包括 i位置)之后都是 1 的最大长度为x。
满足的条件:ans[i + x - 1] - ans[i - 1] + k >= x
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.
Example
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:有n个数(0 或 1)序列,可以执行最多k次操作把 0 改为 1 ,问在满足条件的情况下连续为 1 的序列最大的长度。
解题思路:用二分法。ans[i]记录当前 i 位置之前(包括当前位置),有多少个 1 。
x :从 i 位置开始(包括 i位置)之后都是 1 的最大长度为x。
满足的条件:ans[i + x - 1] - ans[i - 1] + k >= x
#include<bits/stdc++.h> using namespace std; const int MAXN = 3 * 100000 + 5; int s[MAXN]; int ans[MAXN]; int n,k,p = -1 ; bool slove(int x){ for(int i = 0;i + x - 1 < n;i++){ if(ans[i + x - 1] - ans[i - 1] + k >= x){ p = i; return true; } } return false; } int main(){ int l,r,mid; cin>>n>>k; for(int i = 0;i < n;i++){ cin>>s[i]; ans[i] = ans[i - 1] + (s[i] == 1); } l = 0,r = n + 1; while(r > l + 1){ mid = (r + l) / 2; if(slove(mid)) l = mid; else r = mid; } cout<<l<<endl; for(int i = 0;i < p;i++) cout<<s[i]<<' '; for(int i = p;i < p + l;i++) cout<<'1'<<' '; for(int i = max(p + l, 0);i < n;i++)cout<<s[i]<<' '; }
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