ZOJ 3349 Special Subsequence 简单DP + 线段树

同 HDU 2836 只不过改成了求最长子串。

DP+线段树单点修改+区间查最值。

#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <algorithm>

#define lson l, m, rt << 1
#define rson m + 1, r, rt << 1 | 1

using namespace std;

const int MAXN = 100100;

int n, d;
int val[MAXN];
int num[MAXN];
int dp[MAXN];

int maxi[ MAXN << 2 ];

void pushUp( int rt )
{
    maxi[rt] = max( maxi[rt << 1], maxi[rt << 1 | 1] );
    return;
}

void Update( int L, int c, int l, int r, int rt )
{
    if ( l == L && L == r )
    {
        maxi[rt] = c;
        return;
    }

    int m = ( l + r ) >> 1;
    if ( L <= m ) Update( L, c, lson );
    else Update( L, c, rson );
    pushUp( rt );
    return;
}

int Query( int L, int R, int l, int r, int rt )
{
    if ( L <= l && r <= R )
        return maxi[rt];

    int m = ( l + r ) >> 1;

    int res = 0;
    if ( L <= m ) res = max( res, Query( L, R, lson ) );
    if ( R > m )  res = max( res, Query( L, R, rson ) );

    return res;
}

int main()
{
    while ( ~scanf( "%d%d", &n, &d ) )
    {
        for ( int i = 1; i <= n; ++i )
        {
            scanf( "%d", &val[i] );
            num[i] = val[i];
        }

        sort( num + 1, num + 1 + n );
        int cnt = unique( num + 1, num + n + 1 ) - num - 1;

        dp[0] = 0;
        memset( maxi, 0, sizeof(maxi) );
        int ans = 0;

        for ( int i = 1; i <= n; ++i )
        {
            int id = lower_bound( num + 1, num + cnt + 1, val[i] ) - num;
            int left = lower_bound( num + 1, num + cnt + 1, val[i] - d ) - num;
            int right = upper_bound( num + 1, num + cnt + 1, val[i] + d ) - num - 1;
            dp[i] = Query( left, right, 1, n, 1 ) + 1;
            ans = max( ans, dp[i] );
            Update( id, dp[i], 1, n, 1 );
        }
        printf( "%d
", ans );
    }
    return 0;
}