Codeforces Round #254 (Div. 2)B. DZY Loves Chemistry

B. DZY Loves Chemistry

time limit per test

1 second

memory limit per test

256 megabytes

input

standard input

output

standard output

DZY loves chemistry, and he enjoys mixing chemicals.

DZY has n chemicals, and m pairs of them will react.
He wants to pour these chemicals into a test tube, and he needs to pour them in one by one, in any order.

Let's consider the danger of a test tube. Danger of an empty test tube is 1. And every time when DZY pours a chemical, if there are already one or more chemicals
in the test tube that can react with it, the danger of the test tube will be multiplied by 2. Otherwise the danger remains as it is.

Find the maximum possible danger after pouring all the chemicals one by one in optimal order.

Input

The first line contains two space-separated integers n and m .

Each of the next m lines contains two space-separated integers xi and yi (1 ≤ xi < yi ≤ n).
These integers mean that the chemical xi will
react with the chemical yi.
Each pair of chemicals will appear at most once in the input.

Consider all the chemicals numbered from 1 to n in some order.

Output

Print a single integer — the maximum possible danger.

Sample test(s)

input

1 0

output

1

input

2 1
1 2

output

2

input

3 2
1 2
2 3

output

4

思路：依据反应关系找到全部的集合，再在集合中求得结果（由于n<=50。所以用__int64）

代码：

#include <stdio.h>
int father[55];
int find(int x)
{
	if (father[x] == x)
		return x;
	else
		return (father[x] = find(father[x]));
}
void merge(int a, int b)
{
	int x, y;
	x = find(a);
	y = find(b);
	if (x != y)
		father[x] = y;
}
int main()
{
	int n, m;
	while (scanf("%d%d", &n, &m) != EOF)
	{
		for (int i = 1; i <= n; i++)
			father[i] = i;
		while (m--){
			int x, y;
			scanf("%d%d", &x, &y);
			merge(x, y);
		}
		__int64 ans = 1;
		for (int i = 1; i <= n; i++){
			int fa = father[i];
			if (fa == i){
				int s = 2;
				for (int j = 1; j <= n; j++)
				if (find(j) == fa&&i != j){
					ans = ans*s;
				}
			}
		}
		printf("%I64d\n", ans);
	}
	return 0;
}