Codeforces Round #386 (Div. 2) E

题意：给你n个数，和m，让我们从1-m选数字，使得n个数奇数和偶数个数相同切各不相同

思路：模拟

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

int n,m;
set<ll > s;
map<ll ,int > ma;
ll b[200005];
ll a[200005];
int main(){
    cin>>n>>m;
   ll x;
    for(int i=1;i<=n;i++){
        scanf("%lld",&x);
        a[i]=x;
        s.insert(x);
    }
    int s1=0,s2=0;
    for(set<ll >::iterator it=s.begin();it!=s.end();it++){
        ma[*it]++;
        if(*it&1) s1++;
        else s2++;
    }
    s1=n/2-s1;
    s2=n/2-s2;
    if(s1<0) s1=0;
    if(s2<0) s2=0;
    int sum=0;
    int l=0;
    for(int i=1;i<=m;i+=2){
        if(s1==0) break;
        if(!ma[i]){
            s1--;
            b[++l]=i;
            sum++;
        }

    }
    for(int i=2;i<=m;i+=2){
        if(s2==0) break;
        if(!ma[i]){
           b[++l]=i;
            s2--;sum++;
        }

    }

    if(s1||s2) cout<<-1<<endl;
    else {
        int r=1;
        int sum1=0,sum2=0;
        cout<<sum<<endl;
        for(int i=1;i<=n;i++){
            int t=0;
            if(ma[a[i]]){
                if(a[i]&1){
                    if(sum1<n/2) {
                        printf("%d ",a[i]);
                        sum1++;ma[a[i]]=0;t=1;
                    }
                }
                else {
                    if(sum2<n/2){
                        printf("%d ",a[i]);
                        sum2++;ma[a[i]]=0;t=1;
                    }
                }
            }
            if(!t) printf("%d ",b[r++]);
        }
        printf("
");
    }
}