[Noi2010] D1T2 超级钢琴 (ST表 线段树 主席树)

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
#include <map>
#include <queue>
#define INF 0x3f3f3f3f
using namespace std;

const int N = 500005;

inline void read( int &res )
{
char ch = getchar(); res = 0; int flag = 1;
while(ch < '0' || ch > '9') {if(ch == '-') flag = -1; ch = getchar();}
while(ch >= '0' && ch <= '9') res = res * 10 + ch - 48, ch = getchar();
res *= flag;
}

int n, k, L, R, a
, sum
, rmq
[21], llg
;

void Pre()
{
for(int i = 1; i <= n; ++i) rmq[i][0] = i;
for(int k = 1; k <= 19; ++k)
for(int i = 1; i + (1 << k) - 1 <= n; ++i)
if(sum[rmq[i][k - 1]] > sum[rmq[i + (1 << (k - 1))][k - 1]])
rmq[i][k] = rmq[i][k - 1];
else rmq[i][k] = rmq[i + (1 << (k - 1))][k - 1];
}

int Query( int L, int R )
{
int k = llg[R - L + 1];
if(sum[rmq[L][k]] > sum[rmq[R - (1 << k) + 1][k]])
return rmq[L][k];
else return rmq[R - (1 << k) + 1][k];
}

struct Node
{
int lf, rg, pos, tmp;
Node() {    }
Node( int lf, int rg, int pos, int tmp ) : lf(lf), rg(rg), pos(pos), tmp(tmp) { }
bool operator < ( const Node &g ) const
{
return sum[pos] - sum[tmp - 1] < sum[g.pos] - sum[g.tmp - 1];
}
};

priority_queue< Node > que;

int main()
{

read(n), read(k), read(L), read(R);
for(int i = 2; i <= n; ++i) llg[i] = llg[i >> 1] + 1;
for(int i = 1; i <= n; ++i)
read(a[i]), sum[i] = sum[i - 1] + a[i];
Pre();
for(int i = 1; i + L - 1 <= n; ++i)
{
int ps = min(i + R - 1, n);
int as = Query(i + L - 1, ps);
que.push(Node(i + L - 1, ps, as, i));
}
long long ans = 0;
for(int i = 1; i <= k; ++i)
{
Node chs;
chs = que.top();
ans += (long long)sum[chs.pos] - sum[chs.tmp - 1];
que.pop();
int lf = chs.lf, rg = chs.rg;
if(chs.pos > lf) que.push(Node(lf, chs.pos - 1, Query(lf, chs.pos - 1), chs.tmp));
if(chs.pos < rg) que.push(Node(chs.pos + 1, rg, Query(chs.pos + 1, rg), chs.tmp));
}
cout << ans << endl;
return 0;
}
/*
4 3 2 3
3
2
-6
8
*/