Codeforces 760B Frodo and pillows

题目链接：http://codeforces.com/problemset/problem/760/B

题意：n个床位，m个枕头，第k个位置最多有多少个枕头，其中相邻之间的差<=1;

第k个位置最大，那么两边只能是-1，-2，-3下走。

二分查找。

 1 #include <bits/stdc++.h>
 2 
 3 using namespace std;
 4 
 5 long long n,m,k;
 6 
 7 int Slove(long long mid) {
 8     long long sum = 0;
 9     if(k>=mid)
10     {
11         sum+=(1+mid)*mid/2;
12         sum+=(k-mid);
13     }
14     if(k<mid) {
15         sum+=((mid-k+1)+mid)*k/2;
16     }
17 
18     if(k+(mid-1)<=n) {
19         sum+=(1+mid)*mid/2;
20         sum+=n-(k+(mid-1));
21     }
22 
23     if(k+(mid-1)>n) {
24         sum+=(mid+(mid-n+k))*(n-k+1)/2;
25     }
26     if(sum-mid<=m) return 1;
27     else return 0;
28 }
29 
30 int main()
31 {
32     //scanf("%d%d%d",&n,&m,&k);
33     cin>>n>>m>>k;
34     long long ans = 0;
35     long long l = 1;
36     long long r = m;
37     while(l<=r) {
38 
39         long long mid = (l+r)/2;
40         if(Slove(mid)==1) {
41             ans = mid;
42             l = mid+1;
43         }
44         else r = mid-1;
45     }
46     cout<<ans<<endl;
47     return 0;
48 }

 

转载于:https://www.cnblogs.com/TreeDream/p/6347549.html