Submission #390636

#	Time	Username	Problem	Language	Result	Execution time	Memory
390636		WLZ	Horses (IOI15_horses)	C++14	57 / 100	1594 ms	89564 KiB

horses

#include "horses.h"
#include <bits/stdc++.h>
using namespace std;

const int MOD = (int) 1e9 + 7;

int add(int a, int b) {
  if (a + b >= MOD) return a + b - MOD;
  return a + b;
}

int mul(int a, int b) {
  return (long long) a * b % MOD;
}

int n;
vector<int> x, y;
set<int> st;

struct node {
  int l, r, mx, pr;
  node *left, *right;
} *root;

node *build(int l, int r) {
  if (l == r) return new node{l, r, y[l], x[l], nullptr, nullptr};
  node *left = build(l, (l + r) / 2);
  node *right = build((l + r) / 2 + 1, r);
  return new node{l, r, max(left->mx, right->mx), mul(left->pr, right->pr), left, right};
}

void update(node *cur, int pos) {
  if (cur->l == cur->r) {
    cur->mx = y[pos], cur->pr = x[pos];
    return;
  }
  if (pos <= cur->left->r) update(cur->left, pos);
  else update(cur->right, pos);
  cur->mx = max(cur->left->mx, cur->right->mx);
  cur->pr = mul(cur->left->pr, cur->right->pr);
}

int query_mx(node *cur, int l, int r) {
  if (cur->l > r || cur->r < l) return 0;
  if (l <= cur->l && cur->r <= r) return cur->mx;
  return max(query_mx(cur->left, l, r), query_mx(cur->right, l, r));
}

int query_pr(node *cur, int l, int r) {
  if (cur->l > r || cur->r < l) return 1;
  if (l <= cur->l && cur->r <= r) return cur->pr;
  return mul(query_pr(cur->left, l, r), query_pr(cur->right, l, r));
}

int calc_ans() {
  int i = 0, prev = n, best = -1, best_next = -1;
  st.insert(0);
  for (auto it = st.rbegin(); it != st.rend() && i < 30; it++, i++) {
    if (best == -1) {
      best = *it, best_next = prev;
      continue;
    }
    int cost = query_mx(root, *it, prev - 1);
    long long cur = query_mx(root, best, best_next - 1);
    bool better = true;
    for (auto it2 = st.lower_bound(best); *it2 != *it; it2--) {
      cur *= x[*it2];
      if (cur > cost) {
        better = false;
        break;
      }
    }
    if (better) best = *it, best_next = prev;
  }
  return mul(query_pr(root, 0, best), query_mx(root, best, best_next - 1));
}

int init(int N, int X[], int Y[]) {
  n = N;
  x.assign(X, X + n);
  y.assign(Y, Y + n);
  for (int i = 0; i < n; i++) if (x[i] != 1) st.insert(i);
  root = build(0, n - 1);
  return calc_ans();
}

int updateX(int pos, int val) {	
  if (x[pos] != val) {
    if (val != 1) st.insert(pos);
    else if (st.count(pos)) st.erase(pos);
    x[pos] = val;
    update(root, pos);
  }
  return calc_ans();
}

int updateY(int pos, int val) {
  y[pos] = val;
  update(root, pos);
  return calc_ans();
}

Compilation message (stderr)

horses.cpp: In function 'int mul(int, int)':
horses.cpp:13:28: warning: conversion from 'long long int' to 'int' may change value [-Wconversion]
   13 |   return (long long) a * b % MOD;
      |          ~~~~~~~~~~~~~~~~~~^~~~~

• Subtask 1: 17 / 17
• Subtask 2: 17 / 17
• Subtask 3: 0 / 20
• Subtask 4: 23 / 23
• Subtask 5: 0 / 23