Submission #1665502

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Source Code Expand

#include <bits/stdc++.h>
using namespace std;

typedef long long ll;

vector<int> ch[100005];
int col[100005];
int n, m;

bool impossible()
{
	bool had = false;
	for (int i = 0;i < n;i++) if (ch[i].size() >= 2)
	{
		if (had) return false;
		had = true;
	}
	return true;
}

bool dfs(int at)
{
	for (int u: ch[at])
	{
		int c = !col[at];
		if (col[u] == 2)
		{
			col[u] = c;
			if (!dfs(u)) return false;
		} else if (col[u] != c)
			return false;
	}
	return true;
}

bool bipartite()
{
	for (int i = 0;i < n;i++) col[i] = 2;
	col[0] = 0;
	return dfs(0);
}

int main()
{
	scanf("%d%d", &n, &m);
	for (int i = 0;i < m;i++)
	{
		int a, b; scanf("%d%d", &a, &b);
		--a, --b;
		ch[a].push_back(b);
		ch[b].push_back(a);
	}
	if (impossible()) printf("0\n");
	else if (!bipartite()) printf("%lld\n", 1ll*n*(n-1)/2-m);
	else
	{
		ll a = 0, b = 0;
		for (int i = 0;i < n;i++) (col[i]?a:b)++;
		printf("%lld\n", a*b-m);
	}
	return 0;
}

Submission Info

Compile Error

./Main.cpp: In function ‘int main()’:
./Main.cpp:45:23: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d", &n, &m);
                       ^
./Main.cpp:48:34: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
   int a, b; scanf("%d%d", &a, &b);
                                  ^

Judge Result