显然可以发现：
我们sort之后，把奇数位的先按顺序拿出来，然后再把偶数位的按照反顺序拿出来，这样就可以保证答案最小。
代码：
/*
code by: zstu wxk
time: 2019/02/24
*/
#include<bits/stdc++.h>
using namespace std;
#define Fopen freopen("_in.txt","r",stdin); freopen("_out.txt","w",stdout);
#define LL long long
#define ULL unsigned LL
#define fi first
#define se second
#define pb push_back
#define lson l,m,rt<<1
#define rson m+1,r,rt<<1|1
#define lch(x) tr[x].son[0]
#define rch(x) tr[x].son[1]
#define max3(a,b,c) max(a,max(b,c))
#define min3(a,b,c) min(a,min(b,c))
typedef pair<int,int> pll;
const int inf = 0x3f3f3f3f;
const int _inf = 0xc0c0c0c0;
const LL INF = 0x3f3f3f3f3f3f3f3f;
const LL _INF = 0xc0c0c0c0c0c0c0c0;
const LL mod = (int)1e9+7;
const int N = 1e5 + 100;
int n;
int a[N];
vector<int> vc1, vc2;
void Ac(){
for(int i = 1; i <= n; ++i)
scanf("%d", &a[i]);
sort(a+1, a+1+n);
for(int i = 1; i <= n; i += 2)
vc1.pb(a[i]);
for(int i = 2; i <= n; i += 2)
vc2.pb(a[i]);
reverse(vc2.begin(), vc2.end());
for(int x : vc1) printf("%d ", x);
for(int x : vc2) printf("%d ", x);
puts(""); return ;
}
int main(){
while(~scanf("%d", &n)){
Ac();
}
return 0;
}
View Code