Submission #6375849

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Source Code Expand

#include <bits/stdc++.h>
#define inf 4294967295
#define MAXN 500100
#define LL long long
#define pi acos(-1)
#define MOD 332748118

using namespace std;

struct pp{
	int x,y;
} ans[MAXN];

int ot[MAXN],ne[MAXN],g[MAXN],e,d[MAXN],f[MAXN];

void add(int x,int y){
	ot[++e]=y,ne[e]=g[x],g[x]=e;
	ot[++e]=x,ne[e]=g[y],g[y]=e;	
}

int n,m;
set<int> a,b;

int main()
{
	scanf("%d%d",&n,&m);
	for (int i = 1; i <= m; ++i){
		int x,y;
		scanf("%d%d",&x,&y);	
		add(x,y);
		d[x]++,d[y]++;
	}
	for (int i = 1; i <= n; ++i) f[i] = 0;
	for (int i = 1; i <= n; ++i) if (d[i]%2) a.insert(i);else b.insert(i);
	int tot=0;
	set<int>::iterator it;
	int pp = 1;
	while (tot<m){
		it=b.begin();
		if (it==b.end()){
			pp = 0;
			break;
		}
		int x = *it;
		f[x] = 1;
		b.erase(x);
		//cout << x << " " << d[x] << endl;
		for (int p = g[x]; p; p = ne[p]){
			int y = ot[p];
			if (!f[y]){
				ans[++tot].x = x, ans[tot].y = y;
				if (d[y]%2){
					a.erase(y);d[y]--;
					b.insert(y);	
				} else {
					b.erase(y);d[y]--;
					a.insert(y);	
				}
			}
		}
	}
	if (!pp) puts("-1");
	else {
		for (int i = 1; i <= m; ++i) printf("%d %d\n",ans[i].x,ans[i].y);	
	}
	return 0;
}

Submission Info

Compile Error

./Main.cpp: In function ‘int main()’:
./Main.cpp:26:21: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d",&n,&m);
                     ^
./Main.cpp:29:22: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d",&x,&y); 
                      ^

Judge Result