hdu 1325 Is It A Tree? (树、node = edge + 1、入度 <= 1、空树)
Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 29483 Accepted Submission(s): 6775
A tree is a well-known data structure that is either empty (null, void, nothing) or is a set of one or more nodes connected by directed edges between nodes satisfying the following properties.
There is exactly one node, called the root, to which no directed edges point.
The input will consist of a sequence of descriptions (test cases) followed by a pair of negative integers. Each test case will consist of a sequence of edge descriptions followed by a pair of zeroes Each edge description will consist of a pair of integers; the first integer identifies the node from which the edge begins, and the second integer identifies the node to which the edge is directed. Node numbers will always be greater than zero.
For each test case display the line ``Case k is a tree." or the line ``Case k is not a tree.", where k corresponds to the test case number (they are sequentially numbered starting with 1).
6 8 5 3 5 2 6 4
5 6 0 0
8 1 7 3 6 2 8 9 7 5
7 4 7 8 7 6 0 0
3 8 6 8 6 4
5 3 5 6 5 2 0 0
-1 -1
Case 1 is a tree.
Case 2 is a tree.
Case 3 is not a tree.
C/C++:
#include <map>
#include <queue>
#include <cmath>
#include <vector>
#include <string>
#include <cstdio>
#include <cstring>
#include <climits>
#include <iostream>
#include <algorithm>
#define INF 0xffffff
using namespace std; const int my_max = ;
int a, b, my_node[my_max], my_in[my_max]; int main()
{
int t = ;
while (scanf("%d%d", &a, &b), a >= && b >= )
{
if (a == && b == )
{
printf("Case %d is a tree.\n", t ++);
continue;
} memset(my_node, , sizeof(my_node));
memset(my_in, , sizeof(my_in)); int my_edge = , my_flag = ;
my_node[a] = my_node[b] = my_in[b] = ;
while (scanf("%d%d", &a, &b), a || b)
{
if (my_in[b])
my_flag = ;
my_node[a] = my_node[b] = my_in[b] = ;
my_edge ++;
} if (my_flag)
{
printf("Case %d is not a tree.\n", t ++);
continue;
}
int my_node_cnt = ;
for (int i = ; i < my_max; ++ i)
{
if (my_node[i]) my_node_cnt ++;
}
if (my_node_cnt == my_edge + )
printf("Case %d is a tree.\n", t ++);
else
printf("Case %d is not a tree.\n", t ++);
}
return ;
}
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