PTA A1003&A1004

第二天

A1003 Emergency (25 分)

题目内容

As an emergency rescue team leader of a city, you are given a special map of your country. The map shows several scattered cities connected by some roads. Amount of rescue teams in each city and the length of each road between any pair of cities are marked on the map. When there is an emergency call to you from some other city, your job is to lead your men to the place as quickly as possible, and at the mean time, call up as many hands on the way as possible.

Input Specification:

Each input file contains one test case. For each test case, the first line contains 4 positive integers: N (≤500) - the number of cities (and the cities are numbered from 0 to N−1), M - the number of roads, C₁ and C₂ - the cities that you are currently in and that you must save, respectively. The next line contains N integers, where the i-th integer is the number of rescue teams in the i-th city. Then M lines follow, each describes a road with three integers c₁, c₂ and L, which are the pair of cities connected by a road and the length of that road, respectively. It is guaranteed that there exists at least one path from C₁ to C₂.

Output Specification:

For each test case, print in one line two numbers: the number of different shortest paths between C₁ and C₂, and the maximum amount of rescue teams you can possibly gather. All the numbers in a line must be separated by exactly one space, and there is no extra space allowed at the end of a line.

Sample Input:

5 6 0 2

1 2 1 5 3

0 1 1

0 2 2

0 3 1

1 2 1

2 4 1

3 4 1

Sample Output:

2 4

单词

emergency

英 /ɪ'mɜːdʒ(ə)nsɪ/ 美 /ɪ'mɝdʒənsi/

n. 紧急情况；突发事件；非常时刻

adj. 紧急的；备用的

rescue

英 /'reskjuː/ 美 /'rɛskju/

n. 营救，解救，援救；营救行动

v. 营救，援救；（非正式）防止……丢失

scattered

英 /'skætəd/ 美 /'skætɚd/

adj. 分散的；散乱的

at the mean time

同时

call up

打电话给；召集；使想起；提出

as many hands

尽可能多的人手

guarantee

英 /gær(ə)n'tiː/ 美 /,ɡærən'ti/

n. 保证；担保；保证人；保证书；抵押品

vt. 保证；担保

题目分析

本题是正常的单源最短路问题，使用Dijkstra算法即可解决，只不过在刷新dist（到达每一点的最短路）的时候需要顺便需要刷新num（最短路的条数）与rescue（到达某一点的救援队数量）的数量，关于最短路的条数num，我一开始想的比较简单，只使用了一个整型变量来监测到达终点时的最短路条数，实际上关于最短路的条数和最短路的长度和救援队的数量一样需要不断刷新才能得到最后的结果。

具体代码

#include&ltstdio.h&gt
#include&ltstdlib.h&gt
#include&ltlimits.h&gt
#define MAXSIZE 500

int road[MAXSIZE][MAXSIZE];
int team[MAXSIZE];
int rescue[MAXSIZE];
int is_collect[MAXSIZE];
int is_visited[MAXSIZE];
int dist[MAXSIZE];
int num[MAXSIZE];
int N, M, C1, C2;

void Dijkstra();

int main(void)
{
	scanf("%d %d %d %d", &N, &M, &C1, &C2);
	for (int i = 0; i  rescue[i])
						rescue[i] = rescue[m] + team[i];
				}
				is_visited[i] = 1;
			}
		}
	}
}

参考博客

1003. Emergency (25)-PAT甲级真题（Dijkstra算法）

A1004 Counting Leaves (30 分)

题目内容

A family hierarchy is usually presented by a pedigree tree. Your job is to count those family members who have no child.

Input Specification:

Each input file contains one test case. Each case starts with a line containing 0<N<100, the number of nodes in a tree, and M (<N), the number of non-leaf nodes. Then M lines follow, each in the format:

ID K ID[1] ID[2] ... ID[K]

where ID is a two-digit number representing a given non-leaf node, K is the number of its children, followed by a sequence of two-digit ID's of its children. For the sake of simplicity, let us fix the root ID to be 01.

The input ends with N being 0. That case must NOT be processed.

Output Specification:

For each test case, you are supposed to count those family members who have no child for every seniority level starting from the root. The numbers must be printed in a line, separated by a space, and there must be no extra space at the end of each line.

The sample case represents a tree with only 2 nodes, where 01 is the root and 02 is its only child. Hence on the root 01 level, there is 0 leaf node; and on the next level, there is 1 leaf node. Then we should output 0 1 in a line.

Sample Input:

2 1

01 1 02

Sample Output:

0 1

单词

hierarchy

英 /'haɪərɑːkɪ/ 美 /'haɪərɑrki/

n. 层级；等级制度

sake

英 /seɪk/ 美 /sek/

n. 目的；利益；理由；日本米酒

n. (Sake)人名；(罗)萨克；(日)酒(姓)

processed

英 /p'rəsest/ 美 /p'rəsest/

adj. （食品）经过特殊加工的；精制的；（矿石等）处理过的

v. 加工；审核；处理（数据）；列队行进；冲印（照片）；把（头发）弄成直发（process 的过去式及过去分词）

supposed

英 /sə'pəʊzd/ 美 /sə'pozd/

v. 认为，推断；假定，设想；（婉转表达）我看，要不；必须做；（理论）要求以……为前提（suppose 的过去式和过去分词）

adj. 假定的，据说的；被要求的；被允许的；坚信的，期望的

seniority

英 /siːnɪ'ɒrɪtɪ/ 美 /,sinɪ'ɔrəti/

n. 年长；级别、职位高；资历；（前任者、老资格的）特权

题目分析

本题最大的问题是英文并不能读懂。。。。。题目的大意是给定一个树的结点和非叶子结点数量，以及每个非叶子结点的儿子数量和编号，要求按层次输出每一层的叶子结点数量。

首先题目并未说明这棵树到底是说明树，所以并不能把它当成一个二叉树，普通树的物理表示方法其实我很少接触和实践，所以用了何老师说的儿子-兄弟表示法。

然后就是计算每一层的叶子结点的数量，我用一个整型数组来存储每一层的数量，然后使用递归计算每层的数量。最后再一起输出。具体代码如下。

具体代码

#include&ltstdio.h&gt
#include&ltstdlib.h&gt

struct node
{
	int son;
	int brother;
};

struct node tree[100];
int not_root[100];
int N, M;
int max = -1;
int leaf[100];

void count_leaf(int root, int level);

int main(void)
{
	scanf("%d %d", &N, &M);
	for (int i = 0; i  max)
			max = level;
		int last = root;
		while (last != 0)
		{
			if (tree[last].son == 0)
				leaf[level]++;
			else
				count_leaf(tree[last].son, level + 1);
			last = tree[last].brother;
		}
	}
}