初始l为0有事吗

虽然答案是对的

但看到别人都是初始为1

#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define mx(a,b) a>b?a:b
#define mn(a,b) a<b?a:b
#define il inline
int belong, n, m;
int ans, cnt[1000010];
int answer[1000010];
int a[1000010];
struct N
{
	int l, r;
	int id;
}q[1000010];
il bool cmp(N a, N b)
{
	return (a.l / belong) ^ (b.l / belong) ? a.l < b.l : ( ( (a.l / belong) & 1) ? a.r < b.r : a.r > b.r);
}
il int read()
{
	int s = 0, f = 1;
	char ch = getchar();
	while (!isdigit(ch))
	{
		if (ch == '-') f = -1;
		ch = getchar();
	}
	while (isdigit(ch))
	{
		s = (s << 1) + (s << 3) + (ch ^ 48);
		ch = getchar();
	}
	return s * f;
}
il void write(int x)
{
	if (x<0)
	{
		putchar('-');
		x=-x;
	}
	if (x>9)
		write(x/10);
	putchar(x%10+48);
	return;
}
int main()
{
	n = read();
	for(int  i = 1; i <= n; ++i)
		a[i] = read();
	m = read();
	belong = 1700;
	for(int i = 1; i <= m; ++i)
		{
			q[i].l = read();
			q[i].r = read();
			q[i].id = i;
		}
	std::sort(q + 1, q + m + 1, cmp);
	int l = 0, r = 0;
	for(int i = 1; i <= m; ++i)
	{
		int ql = q[i].l, qr = q[i].r;
		while(l < ql) ans -= !--cnt[a[l++]];
		while(l > ql) ans += !cnt[a[--l]]++;
		while(r < qr) ans += !cnt[a[++r]]++;
		while(r > qr) ans -= !--cnt[a[r--]];
		answer[q[i].id] = ans;
	}
	for(int i = 1; i <= m; ++i)
		write(answer[i]), printf("\n");
	return 0;
}

顺便求卡常