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

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。

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
#define N 50010
int n,m,L,a[N];
bool check(int lim){
    int k=0;
    for(int i=1,j=0;i<=n;++i){
        if(a[i]-a[j]<lim) ++k;
        else j=i;
    }return k<=m;
}
int main(){
    scanf("%d%d%d",&L,&n,&m); a[++n]=L;
    for(int i=1;i<n;++i) scanf("%d",&a[i]);
    sort(a+1,a+n+1);
    int l=0,r=L;
    while(l<r){
        int mid=l+((r-l)>>1);
        if(check(mid)) l=mid+1;
        else r=mid; 
    }printf("%d",check(l)?l:l-1);
    return 0;
}