带来两题贪心算法的题. 1.给定长度为N的字符串S,要构造一个长度为N的字符串T.起初,T是一个空串,随后反复进行下面两个操作:1.从S的头部删除一个字符,加到T的尾部.2.从S的尾部删除一个字符,加到T的尾部.求你任意采取这两个步骤后能得到的最小字符串T 2.直线上有N个点,点i的位置是xi,这N个点中选择若干个做上标记,对于每个点,在他们距离为R的区域内必须带有标记点,求在满足这个条件的情况下,所需要标记点的最少个数. 1.POJ 3617 Best Cow Line http://poj.…

 Saruman's Army Time Limit:1000MS     Memory Limit:65536KB     64bit IO Format:%I64d & %I64u Submit Status Practice POJ 3069 Appoint description:  System Crawler  (2015-04-27) Description Saruman the White must lead his army along a straight path fro…

Saruman's Army Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 18794   Accepted: 9222 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 s…

地址 http://poj.org/problem?id=3069 题解 题目可以考虑贪心 尽可能的根据题意选择靠右边的点 注意 开始无标记点 寻找左侧第一个没覆盖的点 再来推算既可能靠右的标记点为一轮 我最开始就是轮次的操作理解错误 结果wa了 ac代码如下 #include <iostream> #include <vector> #include <algorithm> using namespace std; /* poj3069 题目大意:一个直线上有N个点.…

POJ 3069 Saruman's Army(萨鲁曼军) Time Limit: 1000MS   Memory Limit: 65536K [Description] [题目描述] 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, know…

Saruman's Army Time Limit : 2000/1000ms (Java/Other)   Memory Limit : 131072/65536K (Java/Other) Total Submission(s) : 3   Accepted Submission(s) : 2 Problem Description Saruman the White must lead his army along a straight path from Isengard to Helm…

Saruman's Army Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 8477   Accepted: 4317 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 se…

题目连接 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 rang…

简单贪心. 从左边开始,找 r 以内最大距离的点,再在该点的右侧找到该点能覆盖的点.如图. 自己的逻辑有些混乱,最后还是参考书上代码.(<挑战程序设计> P46) /****************************************** Problem: 3069 User: Memory: 668K Time: 16MS Language: G++ Result: Accepted ******************************************/ #inc…

链接:http://poj.org/problem?id=3069 题解 #include<iostream> #include<algorithm> using namespace std; ; int N,R; // N是部队数,R是有效射程 int X[MAX]; void solve(){ sort(X,X+N); ,ans=; while(i<N){ // s是没有被覆盖的最左边的点的位置 int s=X[i++]; //一直向右前进直到距 s的距离大于 R的点,此…

Saruman's Army Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 6688   Accepted: 3424 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 se…

在一条直线上,有n个点.从这n个点中选择若干个,给他们加上标记.对于每一个点,其距离为R以内的区域里必须有一个被标记的点.问至少要有多少点被加上标记 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, am…

Saruman's Army Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 13242   Accepted: 6636 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 s…

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…

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…

Saruman's Army Time Limit: 1000MS   Memory Limit: 65536K Total Submissions: 5989   Accepted: 3056 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 se…

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…

http://poj.org/problem?id=3069 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…

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 …

万恶之源 目录 题意 思路 贪心的原则是什么呢? 错解 正解 代码实现 书上的代码 我的代码 比较一下 问题 题意 给定若干个点的坐标,与范围R.每个点可以选择是否标记,标记后这个点的左右范围R内的所有点也会被标记,求为使所有点被标记,我们要主动标记多少个点. 思路 这题总感觉可以用搜索做,毕竟每个点的状态要么是1要么是0.但这是书上贪心的例题,那肯定得用贪心做啦. 贪心的原则是什么呢? 错解 首先我们的目标是尽可能少的标记,因此我们当然可以希望每次一次性标记的点越多越好,那么我们是不是可以遍历…

2015-09-06 萨鲁曼军队 问题大意:萨鲁曼白想要让他的军队从sengard到Helm’s Deep,为了跟踪他的军队,他在军队中放置了魔法石(军队是一条线),魔法石可以看到前后距离为R的距离,为了让魔法石发挥最大的效益,魔法石戴在军人的身上,问你怎么才能使用最少的石头 问题很清晰,思路也很清晰,这道题挺典型的,就是贪心算法, 很容易想到的就是我们只用在距离内找到最后的点(人),然后把魔法石放到其上面就行了,然后依次类推,最后就可以达到最少的数量 具体可以以2R为一次循环,在前R的区间内我…

直线上有N个点.点i的位置是Xi.从这N个点中选择若干个,给它们加上标记.对每一个点,其距离为R以内的区域里必须又带有标记的点(自己本身带有标记的点,可以认为与其距离为0的地方有一个带有标记的点).在满足这个条件的情况下,希望能为尽可能少的点添加标记.请问至少要有多少点被加上标记? #include "iostream" #include "algorithm" using namespace std; const int MAX_N = 1000; int N=6…

题目描述 Best Cow Line (POJ 3617) 给定长度为N的字符串S,要构造一个长度为N字符串T.T是一个空串,反复执行下列任意操作: 从S的头部删除一个字符,加到T的尾部: 从S的尾部删除一个字符,加到T的尾部: 目标是要构造字典序尽可能小的字符串T. 限制条件 1 <= N <= 2000 字符串 S 只包含大写英文字母 样例输入 N = 6 S = "ACDBCB" 样例输出 ABCBCD (如下图所示进行操作) 思路分析 不断取S的开头和结尾中较小的一…

一.题面 POJ3069 二.题意分析 我的理解是,可以在每个点设置一个监测点,能够监测到范围R内的所有其他点,那么问给出N个点的一维位置,需要在其中挑多少个监测点把所有点都监测到. 贪心解决: 1.先排序. 2.考虑第一个点,因为每个点是必须要监测的,那么第一个点需要被监测到,它可以是监测点,也可以是被监测点.贪心的想,为了能监测更多的点,让第一个点作为被监测的点,且是监测范围内最边界上的点. 3.现在需要考虑,当第一个点往右探测R范围时,最后一个点将是需要设置的监测点. 4.以这个监测点再往…

https://vjudge.net/problem/POJ-3069 弄清楚一点,第一个stone的位置,考虑左右两边都要覆盖R,所以一般情况下不会在左边第一个(除非前两个相距>R). 一开始二层循环外层写的i=1,这样对于数据诸如1 1 1=>0,而其实结果是1. #include<iostream> #include<cstdio> #include<queue> #include<cstring> #include<algorith…

题意:给出指路石的范围,问最小需要几个指路石可以覆盖所有的军队. 题解:排序一遍,然后扫出起始区间和终止区间,就可以求出最小的覆盖数了 ac代码: #include <iostream> #include <algorithm> #include <cstdio> #include <cstring> using namespace std; int main() { cin.sync_with_stdio(false); int n,m; ]; while…

此题的策略是选取可用范围最右边的点,一般来说该点辐射两边,左侧辐射,右侧辐射,所以用两个循环,第一个循环找出该点,第二个循环求出最右边的点 源代码: #include<iostream>#include<algorithm>using namespace std;#define maxn 1100int main(){    int r,n,k=0,num=0,x,a[maxn];    cin>>n;    for(int i=0;i<n;i++) cin>…

The King Time Limit: 2000MS   Memory Limit: 65536K Total Submissions: 7499   Accepted: 4060 Description Once upon a time in a country far away lived a king and he had a big kingdom. He was a very clever king but he had one weakness -- he could count…

http://poj.org/problem?id=1065 题意比较简单,有n跟木棍,事先知道每根木棍的长度和宽度,这些木棍需要送去加工,第一根木棍需要一分钟的生产时间,如果当前木棍的长度跟宽度 都大于前一根木棍,那么这根木棍不需要生产时间,问你最少的生产时间是多少? 首先可以贪心,先按长度 l排序,如果l相同,按宽度w排序. 从i=0开始,每次把接下来的i+1  -  n-1 的没有标记并且长度和宽度大于等于i这根木棍的长度和宽度标记起来. #include<cstdio> #includ…

POJ 2393 题意: 每周可以生产牛奶,每周生产的价格为Ci,每周需要上交的牛奶量Yi,你可以选择本周生产牛奶,也可选择提前几周生产出存储在仓库中(仓库无限大,而且保质期不考虑),每一周存仓库牛奶需要花费S元,让你求出所有周的需求量上交的最少花费. 分析: 因为第 i 周的奶酪,可以在第 i 周生产,也可以在前几周生产,然后储存.通过把s转化为花费,跟原有花费去比较,取一个最小值,这样从头到尾,每一周都可以取得一个花费的最小值.贪心求解. #include<cstdio> #include…