Editorial for Dãy số 1


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Lưu ý: Các code mẫu dưới đây chỉ mang tính tham khảo và có thể không AC được bài tập này

Code mẫu của flashmt

#include <iostream>
#include <algorithm>
#include <cstring>
using namespace std;

int a[333],n,ans,f[333][333];

int main()
{
    cin >> n;
    for (int i=1;i<=n;i++) cin >> a[i];

    for (int i=2;i+ans<=n;i++)
    {
        memset(f,0,sizeof(f));
        for (int j=1;j<i;j++)
            for (int k=i;k<=n;k++)
            {
                f[j][k]=max(f[j-1][k],f[j][k-1]);
                if (a[j]<a[k])
                    f[j][k]=max(f[j][k],f[j-1][k-1]+1);
            }
        ans=max(ans,f[i-1][n]);
    }

    cout << ans << endl;
}

Code mẫu của ladpro98

program kseq1;
uses    math;
const   fi='';
        maxn=303;

var     f:array[0..maxn,0..maxn] of longint;
        a:array[1..maxn] of longint;
        n,i,j,k,res:longint;
        inp:text;
begin
        assign(inp,fi);reset(inp);
        readln(inp,n);
        for i:=1 to n do read(inp,a[i]);
        for i:=2 to n do
        begin
                f[0,i-1]:=0;
                for j:=i-1 to n do f[0,j]:=0;
                for j:=0 to i-1 do f[j,i-1]:=0;
                for j:=1 to i-1 do
                for k:=i to n do
                if a[j]<a[k] then f[j,k]:=f[j-1,k-1]+1
                else    f[j,k]:=max(f[j-1,k],f[j,k-1]);
                res:=max(res,f[i-1,n]);
        end;
        write(res);
end.

Code mẫu của RR

#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;
#define BUFSIZE (1<<12)
char BUF[BUFSIZE+1], *inp=BUF;
#define GETCHAR(INP) { \
    if(!*inp) { \
        if (REACHEOF) return 0;\
        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, a[333], f[333][333];

int main() {
    scanf("%d", &n);
    FOR(i,1,n) scanf("%d", &a[i]);
    int res = 0;
    FOR(gh,2,n) {
        memset(f, 0, sizeof f);
        FOR(i,1,gh-1)
        FOR(j,gh,n) {
            if (a[i] < a[j]) f[i][j] = f[i-1][j-1] + 1;
            else f[i][j] = max(f[i-1][j], f[i][j-1]);

            res = max(res, f[i][j]);
        }
    }
    printf("%d\n", res);
    return 0;
}

Code mẫu của hieult

#include <set>
#include <map>
#include <list>
#include <cmath>
#include <queue>
#include <stack>
#include <cstdio>
#include <string>
#include <vector>
#include <cstdlib>
#include <cstring>
#include <sstream>
#include <iomanip>
#include <iostream>
#include <algorithm>
#include <ctime>
#include <deque>
#include <bitset>
#include <cctype>
#include <utility>

using namespace std;

typedef long long ll;
typedef long double ld;
typedef unsigned int ui;
typedef unsigned long long ull;

#define Rep(i,n) for(int i = 0; i < (n); ++i)
#define Repd(i,n) for(int i = (n)-1; i >= 0; --i)
#define For(i,a,b) for(int i = (a); i <= (b); ++i)
#define Ford(i,a,b) for(int i = (a); i >= (b); --i)
#define Fit(i,v) for(__typeof((v).begin()) i = (v).begin(); i != (v).end(); ++i)
#define Fitd(i,v) for(__typeof((v).rbegin()) i = (v).rbegin(); i != (v).rend(); ++i)
#define mp make_pair
#define pb push_back
#define fi first
#define se second
#define sz(a) ((int)(a).size())
#define all(a) (a).begin(), (a).end()
#define ms(a,x) memset(a, x, sizeof(a))

template<class F, class T> T convert(F a, int p = -1) {
    stringstream ss;
    if (p >= 0)
        ss << fixed << setprecision(p);
    ss << a;
    T r;
    ss >> r;
    return r;
}
template<class T> T gcd(T a, T b) {
    T r;
    while (b != 0) {
        r = a % b;
        a = b;
        b = r;
    }
    return a;
}
template<class T> T lcm(T a, T b) {
    return a / gcd(a, b) * b;
}
template<class T> T sqr(T x) {
    return x * x;
}
template<class T> T cube(T x) {
    return x * x * x;
}
template<class T> int getbit(T s, int i) {
    return (s >> i) & 1;
}
template<class T> T onbit(T s, int i) {
    return s | (T(1) << i);
}
template<class T> T offbit(T s, int i) {
    return s & (~(T(1) << i));
}
template<class T> int cntbit(T s) {
    return s == 0 ? 0 : cntbit(s >> 1) + (s & 1);
}

const int bfsz = 1 << 16;
char bf[bfsz + 5];
int rsz = 0;
int ptr = 0;
char gc() {
    if (rsz <= 0) {
        ptr = 0;
        rsz = (int) fread(bf, 1, bfsz, stdin);
        if (rsz <= 0)
            return EOF;
    }
    --rsz;
    return bf[ptr++];
}
void ga(char &c) {
    c = EOF;
    while (!isalpha(c))
        c = gc();
}
int gs(char s[]) {
    int l = 0;
    char c = gc();
    while (isspace(c))
        c = gc();
    while (c != EOF && !isspace(c)) {
        s[l++] = c;
        c = gc();
    }
    s[l] = '\0';
    return l;
}
template<class T> bool gi(T &v) {
    v = 0;
    char c = gc();
    while (c != EOF && c != '-' && !isdigit(c))
        c = gc();
    if (c == EOF)
        return false;
    bool neg = c == '-';
    if (neg)
        c = gc();
    while (isdigit(c)) {
        v = v * 10 + c - '0';
        c = gc();
    }
    if (neg)
        v = -v;
    return true;
}

typedef pair<int, int> II;
const ld PI = acos(-1.0);
const ld eps = 1e-9;
const int dr[] = { -1, 0, +1, 0};
const int dc[] = { 0, +1, 0, -1};
const int inf = (int) 1e9 + 5;
const ll linf = (ll) 1e16 + 5;
const int mod = (ll) (1e9 + 7 + eps);
#define ok puts("ok")
#define maxn 305

int n, a[maxn], d[maxn][maxn];

int cal(int x){
    int T = min(x, n - x);
    int f[x + 2][T + 2];
    ms(f, 0x3f);
    For(i, 0, x) f[i][0] = x;
    For(i, 0, x - 1) For(j, 0, T) if(f[i][j] < n + 1){
        f[i + 1][j] = min(f[i + 1][j], f[i][j]);
        f[i + 1][j + 1] = min(f[i + 1][j + 1], d[i + 1][f[i][j] + 1]);
    }

    Ford(i, T, 0) if(f[x][i] < n + 1) return i;
    return 0;
}

int main(){
//  freopen("in.txt", "r", stdin);
    cin >> n;
    For(i, 1, n) cin >> a[i];
    For(i, 1, n){
        d[i][n + 1] = n + 1;
        Ford(j, n, i){
            d[i][j] = d[i][j + 1];
            if(a[j] > a[i]) d[i][j] = j;
        }
    }

    int res = 0;
    For(i, 1, n - 1) res = max(res, cal(i));
    cout << res;

}

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