Submission #1004815

#	Submission time	Handle	Problem	Language	Result	Execution time	Memory
1004815	2024-06-21T16:55:11 Z	magikarp23	Horses (IOI15_horses)	C++17	Compilation error	0 ms	0 KB

horses

You're absolutely right, and I apologize for that oversight. You've pointed out a crucial issue: we need to find the true maximum before applying the modulo operation. This is a great catch.
To solve this problem correctly while avoiding overflow, we can use a technique called "modular exponentiation" combined with maintaining the logarithm of our current value. Here's an improved approach:
cppCopy#include <bits/stdc++.h>
#include "horses.h"
using namespace std;

const int MAX_N = 500000 + 1;
const int MOD = 1000000007;

int X_store[MAX_N];
int Y_store[MAX_N];
int N_store;

long long pow_mod(long long base, long long exp) {
    long long result = 1;
    while (exp > 0) {
        if (exp & 1)
            result = (result * base) % MOD;
        base = (base * base) % MOD;
        exp >>= 1;
    }
    return result;
}

int calc_max_profit() {
    vector<long long> log_horses(N_store + 1, 0);
    long long max_log_profit = 0;
    
    for (int i = 0; i < N_store; i++) {
        if (i > 0) log_horses[i] = log_horses[i-1];
        log_horses[i] += log2l(X_store[i]);
        long long log_profit = log_horses[i] + log2l(Y_store[i]);
        max_log_profit = max(max_log_profit, log_profit);
    }
    
    long long base = 2;
    long long exp = max_log_profit;
    return pow_mod(base, exp);
}

int init(int N, int X[], int Y[]) {
    N_store = N;
    for (int i = 0; i < N; i++) {
        X_store[i] = X[i];
        Y_store[i] = Y[i];
    }
    return calc_max_profit();
}

int updateX(int pos, int val) {
    X_store[pos] = val;
    return calc_max_profit();
}

int updateY(int pos, int val) {
    Y_store[pos] = val;
    return calc_max_profit();
}

Compilation message

horses.cpp:1:4: warning: character constant too long for its type
    1 | You're absolutely right, and I apologize for that oversight. You've pointed out a crucial issue: we need to find the true maximum before applying the modulo operation. This is a great catch.
      |    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
horses.cpp:2:179: warning: missing terminating ' character
    2 | To solve this problem correctly while avoiding overflow, we can use a technique called "modular exponentiation" combined with maintaining the logarithm of our current value. Here's an improved approach:
      |                                                                                                                                                                                   ^
horses.cpp:2:179: error: missing terminating ' character
    2 | To solve this problem correctly while avoiding overflow, we can use a technique called "modular exponentiation" combined with maintaining the logarithm of our current value. Here's an improved approach:
      |                                                                                                                                                                                   ^~~~~~~~~~~~~~~~~~~~~~~~
horses.cpp:3:8: error: stray '#' in program
    3 | cppCopy#include <bits/stdc++.h>
      |        ^
horses.cpp:1:1: error: 'You' does not name a type
    1 | You're absolutely right, and I apologize for that oversight. You've pointed out a crucial issue: we need to find the true maximum before applying the modulo operation. This is a great catch.
      | ^~~
horses.cpp: In function 'int calc_max_profit()':
horses.cpp:26:5: error: 'vector' was not declared in this scope
   26 |     vector<long long> log_horses(N_store + 1, 0);
      |     ^~~~~~
horses.cpp:5:1: note: 'std::vector' is defined in header '<vector>'; did you forget to '#include <vector>'?
    4 | #include "horses.h"
  +++ |+#include <vector>
    5 | using namespace std;
horses.cpp:26:12: error: expected primary-expression before 'long'
   26 |     vector<long long> log_horses(N_store + 1, 0);
      |            ^~~~
horses.cpp:30:20: error: 'log_horses' was not declared in this scope
   30 |         if (i > 0) log_horses[i] = log_horses[i-1];
      |                    ^~~~~~~~~~
horses.cpp:31:9: error: 'log_horses' was not declared in this scope
   31 |         log_horses[i] += log2l(X_store[i]);
      |         ^~~~~~~~~~
horses.cpp:31:26: error: 'log2l' was not declared in this scope
   31 |         log_horses[i] += log2l(X_store[i]);
      |                          ^~~~~
horses.cpp:33:26: error: 'max' was not declared in this scope
   33 |         max_log_profit = max(max_log_profit, log_profit);
      |                          ^~~
horses.cpp:38:19: warning: conversion from 'long long int' to 'int' may change value [-Wconversion]
   38 |     return pow_mod(base, exp);
      |            ~~~~~~~^~~~~~~~~~~