• poj 3069


    http://poj.org/problem?id=3069

     

    Description

    Saruman the White must lead 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 be carried by some troop in the army (i.e., palantirs are 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 that each of his minions is within R units of some palantir.

    Input

    The input test file will contain multiple cases. Each test case begins with a single line containing an integer R, the maximum effective range of all palantirs (where 0 ≤ R ≤ 1000), and an integer n, the number of troops in Saruman’s army (where 1 ≤ n ≤ 1000). The next line contains n integers, indicating the positions x1, …, xn of each troop (where 0 ≤ xi ≤ 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.

    题意:

    给出几个点,给出半径,要求尽可能少标记几个点,实现对全部点的覆盖。

    思路:

    按照坐标排序,然后从左向右依次,第一个点是为标记的点找到最有段半径内的点,标记它,然后以标记点向右覆盖,找到第一个没有覆盖掉点,重复上述操作,知道结束。

    #include<iostream>
    #include<algorithm>
    using namespace std;
    int r,n;
    int a[1003];
    int solve(){
        sort(a,a+n);
        int i = 0;
        int ans = 0;
        while(i < n){
            int s = a[i++];
            while(i < n && a[i] <= s + r) i++;
            int troop = a[i-1];
            while(i < n && a[i] <= troop + r) i++;
            ans++;
        }
        return ans;
    }
    int main()
    {
        ///input
        while(cin >> r >> n && (r != -1) && (n != -1)){
            for(int i = 0 ; i < n;i++)
                cin >> a[i];
             ///solve
            int ans = solve();
            ///output
            cout << ans << endl;
        }
    
        return 0;
    }
    View Code
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  • 原文地址:https://www.cnblogs.com/gudygudy/p/8976289.html
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