POJ 3069 Saruman ' s Army

Saruman ' s Army

Time Limit: 1000MS		Memory Limit: 65536K
Total Submissions: 8477		Accepted: 4317

Description

Saruman The white must leads his army along a straight path from Isengard to Helm ' s deep. To keep track of his forces, Saruman distributes seeing stones, known as Palantirs, among the troops. Each Palantir has a maximum effective range of R units, and must is carried by some troop in the army (i.e., Pala Ntirs is not allowed to ' free float ' in mid-air. Help Saruman take control of middle Earth by determining the minimum number of palantirs needed for Saruman to ensure Each of the Minions is within R units of some palantir.

Input

The input test file would contain multiple cases. Each test case begins with a containing a integer R, the maximum effective range of all Palantirs (w Here 0≤ R ≤1000), and a integer n, the number of troops in Saruman ' s Army (where 1≤ n ≤100 0). The next line contains n integers, indicating the positions x1, ..., xn of each troop (where 0≤ x I ≤1000). The End-of-file is marked by a test case with R = n =−1.

Output

For each test case, print a single integer indicating the minimum number of palantirs needed.

Sample Input

0 310 20 2010 770 30 1 7 15 20 50-1-1

Sample Output

24

Hint

In the first test case, Saruman is a palantir at positions and 20. Here, note this a single Palantir with range 0 can cover both of the troops at position 20.

In the second test case, Saruman can place palantirs at position 7 (covering troops at 1, 7, and), Position (Coverin g positions and), position, and position 70. Here, note this palantirs must be distributed among troops and is not allowed to ' free float. ' Thus, Saruman cannot place a palantir at position-cover the troops at positions and 70.

Simple greed.

#include <iostream>#include<stdio.h>#include<algorithm>using namespacestd;inta[1005];intMain () {intR,n;  while(~SCANF ("%d%d", &r,&n) &&r>=0&&n>-0)    {         for(intI=0; i<n;i++) {scanf ("%d", A +i); } sort (A,a+N); intI=0, s=0; intans=0;  while(i<N) {s=a[i++];  while(s+r>=a[i]&&i<n) i++; if(i>n) Break; intp=a[i-1]; Ans++;  while(p+r>=a[i]&&i<n) i++; } cout<<ans<<Endl; }}

View Code

POJ 3069 Saruman ' s Army