bzoj1650 / P2855 [USACO06DEC]河跳房子River Hopscotch / P2678 (noip2015)跳石头

Posted 2021-01-23 kafuuchino

P2855 [USACO06DEC]河跳房子River Hopscotch

二分+贪心

每次二分最小长度，蓝后检查需要去掉的石子数是否超过限制。

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cstring>
 4 #include<algorithm>
 5 using namespace std;
 6 #define N 50010
 7 int n,m,L,a[N];
 8 bool check(int lim){
 9     int k=0;
10     for(int i=1,j=0;i<=n;++i){
11         if(a[i]-a[j]<lim) ++k;
12         else j=i;
13     }return k<=m;
14 }
15 int main(){
16     scanf("%d%d%d",&L,&n,&m); a[++n]=L;
17     for(int i=1;i<n;++i) scanf("%d",&a[i]);
18     sort(a+1,a+n+1);
19     int l=0,r=L;
20     while(l<r){
21         int mid=l+((r-l)>>1);
22         if(check(mid)) l=mid+1;
23         else r=mid; 
24     }printf("%d",check(l)?l:l-1);
25     return 0;
26 }

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