hdu 5014 异或序列

http://acm.hdu.edu.cn/showproblem.php?pid=5014

从最大的一个数开始找能配对使他们的异或值最大的一个数

最后输出

#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <cstring>
#include <string>
#include <queue>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;
#define RD(x) scanf("%d",&x)
#define RD2(x,y) scanf("%d%d",&x,&y)
#define clr0(x) memset(x,0,sizeof(x))
typedef long long LL;

int s[100005],tran[100005];
bool vis[100005];
int tr(int x)
{
    int cnt = 0;
    while(x){
        cnt++;
        x>>=1;
    }
    return (1<<cnt) - 1;
}
int main(){
    int n;
    while(~scanf("%d",&n)){
        for(int i=0;i<=n;i++){
            scanf("%d",&s[i]);
        }
        clr0(vis);
        LL ans = 0;
        for(int x = n;x >= 0;--x){
            if(!vis[x]){
                vis[x] = true;
                int now = 1LL * tr(x);
                int y = now^x;//cout<<x<<','<<y<<endl;
                if(!vis[y]){
                    ans += now<<1;
                    tran[x] = y,tran[y] = x;
                    vis[y] = true;
                }
                else
                    ans += x,tran[x] = x;
            }
        }
        printf("%I64d\n",ans);
        for(int x = 0;x <= n;++x)
            printf("%d%c",tran[s[x]]," \n"[x == n]);
     }
     return 0;
 }