bzoj4525: [Usaco2016 jan]angry cows

bzoj4525: [Usaco2016 jan]angry cows time limit:1 Sec Memory limit:128 MB
Submit:90 solved:71
[Submit] [Status] [Discuss] Description Cow Bessie designed a game: "Angry cows". The prototype of the game is: there are some explosive haystack distributed in some coordinates of a number axis, play a home slingshot to launch a cow to the number line. The shock wave of a cow hitting the axis will cause a nearby haystack to explode. The goal of the game is to play home some cows blow up all the haystack. There are n haystack in the different positions of the axis, coordinates of x1,x2,...., xn. If the player launches the cow to coordinate X with energy R, it will detonate the haystack in radius r and within, i.e. the haystack of the coordinate range [x−r,x+r] will explode. Now there are K-head cows, each cow's energy is r, please calculate if you want to detonate all the haystack, what is the minimum r?

Input first line: 2 integers N (1≤n≤50,000) and K (1≤K≤10). There are n rows, one integer per line: x1,x2,..., xn, range in [0 ... 1,000,000,000].

Output

Outputs the smallest possible r.

Sample Input7 2
20
25
18
8
10
3
1
Sample Output5HINT Source

Two-point answer + greedy verification

#include <bits/stdc++.h>#defineRep (i,l,r) for (int i=l;i<=r;i++)#defineN 50001using namespaceStd;inlineintRead () {intx=0, ch=GetChar ();  while(ch<'0'|| Ch>'9') ch=GetChar ();  while(ch>='0'&&ch<='9') x=x*Ten+ch- -, ch=GetChar (); returnx;}intMain () {intn,k,s[n],l,r,mid,last,now,ans=2147483647; scanf ("%d%d",&n,&k); Rep (I,1, N) s[i]=read (); Sort (S+1, s+1+N); L=1; R=500000000;  while(l<=r) {Mid= (l+r) >>1; now=0; Rep (I,1, K) { Last=s[now+1];  while(s[now+1]-last<=mid*2&&now<n) + +Now ; }          if(now>=n) Ans=min (ans,mid), r=mid-1;ElseL=mid+1; } printf ("%d", ans);}

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bzoj4525: [Usaco2016 jan]angry cows