Guess Number Higher or Lower II in C++

Suppose we are playing the Guess Game. The rules of the game is as follows −

• Player1 pick a number from 1 to n. player2 have to guess which number is picked by player1.
• Every time player2 guess wrong, player1 will tell whether the number that is picked is higher or lower.

However, when a player guess a particular number x, and another player guess wrong, another player has to pay $x. The game will end, when player2 got the correct answer.

For example if n = 10, and the player1 has taken 8

• In the first round, player2 tells the number is 5, that is wrong, actual number is higher, then he will give $5
• In the second round, player2 tells the number is 7, that is wrong, actual number is higher, then he will give $7
• In the third round, player2 tells the number is 9, that is wrong, actual number is lower, then he will give $9

Now the game ends. So total money given is $5 + $7 + $9 = $21.

To solve this, we will follow these steps −

• create one method called cost, that is taking low, high, another table dp
• if low >= high, return 0
• if dp[low, high] is not -1, then return dp[low, high]
• ans := inf
• for i in range low to high
  • ans := min of ans and (i + max of cost(low, i – 1, dp) and cost(i + 1, high, dp))
• dp[low, high] := ans and return ans
• The actual method will be like −
• make one 2d array called dp of size (n + 1) x (n + 1), and fill this with -1
• return cost(1, n, dp)

Let us see the following implementation to get better understanding −

Example

 Live Demo

#include <bits/stdc++.h>
using namespace std;
class Solution {
public:
   int cost(int low, int high, vector < vector <int> >& dp){
      if(low >= high)return 0;
      if(dp[low][high] != -1)return dp[low][high];
      int ans = INT_MAX;
      for(int i = low; i <= high; i++){
         ans = min(ans, i + max(cost(low, i - 1, dp), cost(i + 1, high, dp)));
      }
      return dp[low][high] = ans;
   }
   int getMoneyAmount(int n) {
      vector < vector <int> > dp(n + 1, vector <int> (n + 1, -1));
      return cost(1, n, dp);
   }
};
int main() {
   Solution ob1;
   cout << ob1.getMoneyAmount(8) << endl;
   return 0;
}

Input

8

Output

12