BZOJ 2006: [NOI2010]超级钢琴

  1 #include <queue>
  2 #include <cstdio>
  3 
  4 inline int nextChar(void)
  5 {
  6     const static int siz = 1024;
  7     
  8     static char buf[siz];
  9     static char *hd = buf + siz;
 10     static char *tl = buf + siz;
 11     
 12     if (hd == tl)
 13         fread(hd = buf, 1, siz, stdin);
 14         
 15     return *hd++;
 16 }
 17 
 18 inline int nextInt(void)
 19 {
 20     register int ret = 0;
 21     register int neg = false;
 22     register int bit = nextChar();
 23     
 24     for (; bit < 48; bit = nextChar())
 25         if (bit == ‘-‘)neg ^= true;
 26         
 27     for (; bit > 47; bit = nextChar())
 28         ret = ret * 10 + bit - 48;
 29         
 30     return neg ? -ret : ret;
 31 }
 32 
 33 const int siz = 500005;
 34 
 35 int N, M, L, R;
 36 
 37 int num[siz];
 38 int sum[siz]; 
 39 
 40 int st[siz][25], log[siz];
 41 
 42 inline void preworkRMQ(void)
 43 {
 44     for (int i = 1; i <= N; ++i)
 45         st[i][0] = i;
 46         
 47     for (int i = 1; (1 << i) <= N; ++i)
 48         for (int j = 1; j + (1 << i) - 1 <= N; ++j)
 49         {
 50             int x = st[j][i - 1];
 51             int y = st[j + (1 << (i - 1))][i - 1];
 52             st[j][i] = sum[x] > sum[y] ? x : y;
 53         }
 54         
 55     log[0] = -1;
 56     
 57     for (int i = 1; i <= N; ++i)
 58         log[i] = log[i >> 1] + 1;
 59 }
 60 
 61 inline int query(int l, int r)
 62 {
 63     if (l == r)
 64         return l;
 65         
 66     int t = log[r - l + 1];
 67     
 68     int x = st[l][t];
 69     int y = st[r - (1 << t) + 1][t];
 70     
 71     return sum[x] > sum[y] ? x : y;
 72 }
 73 
 74 struct data
 75 {
 76     int p, t, l, r;
 77     
 78     data(void) {};
 79     data(int a, int b, int c, int d) :
 80         p(a), t(b), l(c), r(d) {};
 81 };
 82 
 83 inline bool operator < (const data &a, const data &b)
 84 {
 85     return sum[a.t] - sum[a.p - 1] < sum[b.t] - sum[b.p - 1];
 86 }
 87 
 88 std::priority_queue<data> h;
 89 
 90 signed main(void)
 91 {
 92     N = nextInt();
 93     M = nextInt();
 94     L = nextInt();
 95     R = nextInt();
 96     
 97     for (int i = 1; i <= N; ++i)
 98         num[i] = nextInt();
 99     
100     for (int i = 1; i <= N; ++i)
101         sum[i] = sum[i - 1] + num[i];
102     
103     preworkRMQ();
104     
105     long long ans = 0;
106     
107     for (int i = 1; i <= N - L + 1; ++i)
108     {
109         int l = i + L - 1;
110         int r = i + R - 1;
111         
112         if (r > N)
113             r = N;
114             
115         h.push(data(i, query(l, r), l, r));
116     }
117     
118     for (int i = 1; i <= M; ++i)
119     {
120         data top = h.top(); h.pop();
121         
122         ans += sum[top.t] - sum[top.p - 1];
123         
124         if (top.t > top.l)
125             h.push(data(top.p, query(top.l, top.t - 1), top.l, top.t - 1));
126         if (top.t < top.r)
127             h.push(data(top.p, query(top.t + 1, top.r), top.t + 1, top.r));
128     }
129     
130     printf("%lld\n", ans);
131 }