Problem p02599 (C++) — buggy submission, verdict: Runtime Error

#include <algorithm>
#include <cstdio>
#include <cstring>
#include <iostream>
using namespace std;
typedef long long ll;

ll N, M;
const ll SIZE = 5000005;
ll c[SIZE];
ll A[SIZE];
ll Next[SIZE];
ll res[5000005];
ll show[5000005];
bool fir[SIZE];

struct Q {
  ll l, r;
  ll pos;
} q[5000005];

ll lowbit(ll k) { return k & (-k); }

void modify(ll n, ll v) {
  while (n <= N) {
    c[n] += v;
    n += lowbit(n);
  }
}

ll sum(ll n) {
  ll ans = 0;
  while (n > 0) {
    ans += c[n];
    n -= lowbit(n);
  }
  return ans;
}

ll cmp(Q a, Q b) { return a.l < b.l; }

int main() {
  cin >> N >> M;
  for (ll i = 1; i <= N; i++)
    cin >> A[i];
  for (ll i = N; i >= 1; i--) {
    if (!show[A[i]]) {
      show[A[i]] = i;
      fir[i] = true;
    } else {
      Next[i] = show[A[i]];
      fir[Next[i]] = false;
      fir[i] = true;
      show[A[i]] = i;
    }
  }
  for (ll i = 1; i <= M; i++) {
    cin >> q[i].l >> q[i].r;
    q[i].pos = i;
  }
  sort(q + 1, q + 1 + M, cmp);

  for (ll i = 1; i <= N; i++)
    if (fir[i]) {
      modify(i, 1);
    }
  ll qtemp = q[1].l;
  ll ptr = 1;
  for (ll i = 1; i <= M; i++) {
    for (; ptr < q[i].l; ptr++) {
      if (fir[ptr]) {
        modify(ptr, -1);
        fir[ptr] = false;
        if (Next[ptr]) {
          fir[Next[ptr]] = true;
          modify(Next[ptr], 1);
        }
      }
    }
    ptr = q[i].l;
    qtemp = q[i].l;
    res[q[i].pos] = sum(q[i].r) - sum(q[i].l - 1);
  }
  for (ll i = 1; i <= M; i++)
    printf("%lld\\n", res[i]);
  return 0;
}


Error: -11

Fixed submission:

#include <bits/stdc++.h>
using namespace std;
const int MAXN = 300100;
const int M = MAXN * 100;
int n, q, tot;
int a[MAXN];
int T[M], lson[M], rson[M], c[M];
int build(int l, int r) {
  int root = tot++;
  c[root] = 0;
  if (l != r) {
    int mid = (l + r) >> 1;
    lson[root] = build(l, mid);
    rson[root] = build(mid + 1, r);
  }
  return root;
}
int update(int root, int pos, int val) {
  int newroot = tot++, tmp = newroot;
  c[newroot] = c[root] + val;
  int l = 1, r = n;
  while (l < r) {
    int mid = (l + r) >> 1;
    if (pos <= mid) {
      lson[newroot] = tot++;
      rson[newroot] = rson[root];
      newroot = lson[newroot];
      root = lson[root];
      r = mid;
    } else {
      rson[newroot] = tot++;
      lson[newroot] = lson[root];
      newroot = rson[newroot];
      root = rson[root];
      l = mid + 1;
    }
    c[newroot] = c[root] + val;
  }
  return tmp;
}
int query(int root, int pos) {
  int ret = 0;
  int l = 1, r = n;
  while (pos < r) {
    int mid = (l + r) >> 1;
    if (pos <= mid) {
      r = mid;
      root = lson[root];
    } else {
      ret += c[lson[root]];
      root = rson[root];
      l = mid + 1;
    }
  }
  return ret + c[root];
}
int main() {
  scanf("%d%d", &n, &q);

  tot = 0;
  for (int i = 1; i <= n; i++)
    scanf("%d", &a[i]);
  T[n + 1] = build(1, n); // 建立一颗空树
  map<int, int> mp;
  for (int i = n; i >= 1; i--) {
    if (mp.find(a[i]) == mp.end()) {
      T[i] = update(T[i + 1], i, 1);
    } else {
      int tmp = update(T[i + 1], mp[a[i]], -1);
      T[i] = update(tmp, i, 1);
    }
    mp[a[i]] = i;
  }
  while (q--) {
    int l, r;
    scanf("%d%d", &l, &r);
    printf("%d\\n", query(T[l], r));
  }

  return 0;
}