NDCCARD - Các lá bài Blackjack

Tác giả: RR

Ngôn ngữ: C++

#include <sstream>
#include <iomanip>
#include <iostream>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <cmath>
#include <algorithm>
#include <vector>
#include <set>
#include <map>
#include <stack>
#include <queue>
#include <string>
#include <deque>
#include <complex>

#define FOR(i,a,b) for(int i=(a),_b=(b); i<=_b; i++)
#define FORD(i,a,b) for(int i=(a),_b=(b); i>=_b; i--)
#define REP(i,a) for(int i=0,_a=(a); i<_a; i++)
#define FORN(i,a,b) for(int i=(a),_b=(b);i<_b;i++)
#define DOWN(i,a,b) for(int i=a,_b=(b);i>=_b;i--)
#define SET(a,v) memset(a,v,sizeof(a))
#define sqr(x) ((x)*(x))
#define ll long long
#define F first
#define S second
#define PB push_back
#define MP make_pair

#define DEBUG(x) cout << #x << " = "; cout << x << endl;
#define PR(a,n) cout << #a << " = "; FOR(_,1,n) cout << a[_] << ' '; cout << endl;
#define PR0(a,n) cout << #a << " = "; REP(_,n) cout << a[_] << ' '; cout << endl;
using namespace std;

//Buffer reading
int INP,AM,REACHEOF;
const int BUFSIZE = (1<<12) + 17;
char BUF[BUFSIZE+1], *inp=BUF;
#define GETCHAR(INP) { \
    if(!*inp && !REACHEOF) { \
        memset(BUF,0,sizeof BUF);\
        int inpzzz = fread(BUF,1,BUFSIZE,stdin);\
        if (inpzzz != BUFSIZE) REACHEOF = true;\
        inp=BUF; \
    } \
    INP=*inp++; \
}
#define DIG(a) (((a)>='0')&&((a)<='9'))
#define GN(j) { \
    AM=0;\
    GETCHAR(INP); while(!DIG(INP) && INP!='-') GETCHAR(INP);\
    if (INP=='-') {AM=1;GETCHAR(INP);} \
    j=INP-'0'; GETCHAR(INP); \
    while(DIG(INP)){j=10*j+(INP-'0');GETCHAR(INP);} \
    if (AM) j=-j;\
}
//End of buffer reading

const long double PI = acos((long double) -1.0);

int n, m;
int bit[500111];
int a[10111];

#define _(x) ((x) & (-(x)))
int update(int u, int k) {
    while (u <= m) {
        bit[u] = max(bit[u], k);
        u += _(u);
    }
}

int get(int u) {
    int res = -1;
    while (u > 0) {
        res = max(res, bit[u]);
        u -= _(u);
    }
    return res;
}

int main() {
    while (scanf("%d%d", &n, &m) == 2) {
        memset(bit, 0, sizeof bit);
        FOR(i,1,n) scanf("%d", &a[i]);
        sort(a+1, a+n+1);

        int res = 0;
        FOR(i,1,n) {
            if (a[i] >= m) break;
            int sum, t;
            FOR(j,i+1,n) {
                sum = a[i] + a[j];
                if (sum >= m) break;

                t = get(m - sum);
                if (t >= 0) {
                    res = max(res, sum + t);
                }
            }
            update(a[i], a[i]);
        }
        printf("%d\n", res);
    }
    return 0;
}

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