River Hopscotch POJ - 3258 （二分）

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import java.util.*;

public class Main{
	Scanner scan=new Scanner(System.in);
	int l,n,m;
	int[] s=new int [50010];
	
	public Main() {
		super();
		input();
		js();
	}
	public void input() {
		l=scan.nextInt();
		n=scan.nextInt();
		m=scan.nextInt();
		s[0]=0;
		for (int i = 1; i <= n; i++) {
			s[i]=scan.nextInt();
		}
		s[n+1]=l;
	}
	public void js() {
		Arrays.sort(s,0,n+2);
		int L=0,R=l ;
		while(L<=R) {
			int mid=L+(R-L)/2, i=0,p=0;

			while(i<=n) {
				int j=i+1;
				while(j<=n+1&&s[j]-s[i]<mid)
					j++;
				p+=j-i-1;
				i=j;
			}

			if(p<=m) {
				L=mid+1;
			}
			else{
				R=mid-1;
			}
		}
		System.out.println(L-1);
	}
	
	public static void main(String[] args) {
		new Main();
	}
}