【题解】

　　二分答案+贪心check.

1 #include
      
        2 #include
       
         3 #include
        
          4 #define LL long long 5 #define rg register 6 #define N 200010 7 using namespace std; 8 int n,m,a[N],l,r,mid; 9 inline int read(){10     int k=0,f=1; char c=getchar();11     while(c<'0'||c>'9')c=='-'&&(f=-1),c=getchar();12     while('0'<=c&&c<='9')k=k*10+c-'0',c=getchar();13     return k*f;14 }15 inline bool check(){16     int sum=1,last=a[1];17     for(rg int i=2;i<=n;i++)if(a[i]-last>=mid){18         sum++;19         last=a[i];20     }21 //    printf("mid=%d sum=%d\n",mid,sum);22     return sum>=m;23 }24 int main(){25     n=read(); m=read();26     for(rg int i=1;i<=n;i++) a[i]=read();27     sort(a+1,a+1+n);28     l=0; r=a[n]-a[1]+1;29     while(l+1
         
          >1;31         if(check()) l=mid; else r=mid;32     }33     printf("%d\n",l);34     return 0;35 }