BZOJ2743 [HEOI2012]采花

本来想做这道题的。。。后来发现根本搞不懂

于是又滚回了BZOJ 1878搞了搞。。。

发现这道题和1878差不多，只是要注意update的时候要加个next

其实我们可以推广到3个、4个、5个（貌似可以用倍增？感觉可以出一道题呢、、、）

然后就没有然后啦~，不要问我为什么用了fread。。。只是无聊了≥v≤~

/**************************************************************
    Problem: 2743
    User: rausen
    Language: C++
    Result: Accepted
    Time:3940 ms
    Memory:56472 kb
****************************************************************/
 
#include <cstdio>
#include <algorithm>
 
#define lowbit(x) x & -x
using namespace std;
const int N = 1000005;
const int Maxlen = 25 * N;
struct data{
    int l, r, w;
    inline bool operator < (const data &x) const {
        return l == x.l ? r < x.r : l < x.l;
    }
} q[N];
 
int n, m, c;
int a[N], next[N], first[N];
int BIT[N];
int ans[N];
 
char buf[Maxlen], *C = buf;
int Len;
inline int read() {
    int x = 0;
    while (*C < '0' || '9' < *C) ++C;
    while ('0' <= *C && *C <= '9')
        x = x * 10 + *C - '0', ++C;
    return x;
}
 
int L, pr[10];
void print(int x) {
    if (!x) {
        puts("0");
        return;
    }
    while (x)
        pr[++L] = x % 10, x /= 10;
    while (L)
        putchar(pr[L--] + '0');
    putchar('
');
}
 
void update(int x, int v) {
    if (!x) return;
    while (x <= n)
        BIT[x] += v, x += lowbit(x);
}
  
int query(int x) {
    int res = 0;
    while (x)
        res += BIT[x], x -= lowbit(x);
    return res;
}
 
int main() {
    int i, l;
    Len = fread(C, 1, Maxlen, stdin);
    buf[Len] = '';
    n = read(), c = read(), m = read();
    for (i = 1; i <= n; ++i)
        a[i] = read();
    for (i = n; i; --i)
        next[i] = first[a[i]], first[a[i]] = i;
    for (i = 1; i <= c; ++i)
        update(next[first[i]], 1);
 
    for (i = 1; i <= m; ++i)
        q[i].l = read(), q[i].r = read(), q[i].w = i;
    sort(q + 1, q + m + 1);
    for (i = l = 1; i <= m; ++i) {
        for (; l < q[i].l; ++l)
            update(next[l], -1), update(next[next[l]], 1);
        ans[q[i].w] = query(q[i].r) - query(q[i].l - 1);
    }
    for (i = 1; i <= m; ++i)
        print(ans[i]);
    return 0;
}