luogu P2709 小B的询问

最新推荐文章于 2025-05-08 18:41:09 发布

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最新推荐文章于 2025-05-08 18:41:09 发布

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原文链接：http://www.cnblogs.com/mrclr/p/10077860.html

本文深入解析了莫队算法的原理与应用，通过具体代码示例，详细讲解了如何在算法竞赛中高效地处理区间查询问题。文章强调了算法中的关键操作——删除和添加元素的顺序，并提供了一个完整的C++代码实现。

嘟嘟嘟

莫队板子。
记住：删除是先删除再移动，添加是先移动在添加！

#include<cstdio>
#include<iostream>
#include<cmath>
#include<algorithm>
#include<cstring>
#include<cstdlib>
#include<cctype>
#include<vector>
#include<stack>
#include<queue>
using namespace std;
#define enter puts("") 
#define space putchar(' ')
#define Mem(a, x) memset(a, x, sizeof(a))
#define rg register
typedef long long ll;
typedef double db;
const int INF = 0x3f3f3f3f;
const db eps = 1e-8;
const int maxn = 5e4 + 5;
inline ll read()
{
  ll ans = 0;
  char ch = getchar(), last = ' ';
  while(!isdigit(ch)) last = ch, ch = getchar();
  while(isdigit(ch)) ans = (ans << 1) + (ans << 3) + ch - '0', ch = getchar();
  if(last == '-') ans = -ans;
  return ans;
}
inline void write(ll x)
{
  if(x < 0) x = -x, putchar('-');
  if(x >= 10) write(x / 10);
  putchar(x % 10 + '0');
}

int n, m, k, S, a[maxn];
struct Node
{
  int L, R, id, b;
  bool operator < (const Node& oth)const
  {
    return b < oth.b || (b == oth.b && R < oth.R);
  }
}q[maxn];
ll cnt = 0, tot[maxn], ans[maxn];

void add(int x)
{
  ll tp = tot[x]++;
  cnt += (tp << 1) + 1;
}
void del(int x)
{
  ll tp = tot[x]--;
  cnt -= (tp << 1) - 1;
}

int main()
{
  n = read(); m = read(); k = read(); S = sqrt(n);
  for(int i = 1; i <= n; ++i) a[i] = read();
  for(int i = 1; i <= m; ++i)
    {
      int L = read(), R = read();
      q[i] = (Node){L, R, i, (L - 1) * S + 1};
    }
  sort(q + 1, q + m + 1);
  for(int i = 1, l = 1, r = 0; i <= m; ++i)
    {
      while(l < q[i].L) del(a[l++]);
      while(l > q[i].L) add(a[--l]);
      while(r < q[i].R) add(a[++r]);
      while(r > q[i].R) del(a[r--]);
      ans[q[i].id] = cnt;
    }
  for(int i = 1; i <= m; ++i) write(ans[i]), enter;
  return 0;
}

转载于:https://www.cnblogs.com/mrclr/p/10077860.html