Number of Ways to Paint N × 3 Grid in C++

Suppose we have grid of size n x 3 and we want to paint each cell of the grid with exactly one of the three colors. The colors are Red, Yellow or Green. Now there is a constraint that is no two adjacent cells have the same color. We have n the number of rows of the grid. We have to find the number of ways we can paint this grid. The answer may be very large so return it modulo 10^9 + 7.

So, if the input is like 1, then the output will be 12

To solve this, we will follow these steps −

• m = 1^9 + 7

• Define a function add(), this will take a, b,

• return ((a mod m) + (b mod m)) mod m

• From the main method do the following −

• a123 := 6, a121 = 6

• for initialize i := 2, when i <= n, update (increase i by 1), do −

  • b121 := add(3 * a121, 2 * a123)

  • b123 := add(2 * a121, 2 * a123)

  • a121 := b121

  • a123 := b123

• return add(a123, a121)

Let us see the following implementation to get better understanding −

Example

 Live Demo

#include <bits/stdc++.h>
using namespace std;
typedef long long int lli;
const lli mod = 1e9 + 7;
class Solution {
   public:
   lli add(lli a, lli b){
      return ((a % mod) + (b % mod)) % mod;
   }
   int numOfWays(int n){
      lli a123 = 6, a121 = 6;
      lli b123, b121;
      for (int i = 2; i <= n; i++) {
         b121 = add(3 * a121, 2 * a123);
         b123 = add(2 * a121, 2 * a123);
         a121 = b121;
         a123 = b123;
      }
      return add(a123, a121);
   }
};
main(){
   Solution ob;
   cout << (ob.numOfWays(3));
}

Input

3

Output

246

Arnab Chakraborty

Updated on 09-Jun-2020 07:19:15

• Related Questions & Answers
• Number of Ways to Paint N × 3 Grid in C++ program
• Ways to paint N paintings such that adjacent paintings don’t have same colors in C++
• Program to count number of ways we can fill 3 x n box with 2 x 1 dominos in Python
• Ways to paint N paintings such that adjacent paintings don’t have same colors in C programming
• Count of different ways to express N as the sum of 1, 3 and 4 in C++
• Program to count the number of ways to distribute n number of candies in k number of bags in Python
• Program to count number of ways we can throw n dices in Python
• Find the Number of Ways to go From One Point to Another in a Grid using C++
• Program to find sum of series 1*2*3 + 2*3*4+ 3*4*5 + . . . + n*(n+1)*(n+2) in C++
• 3 ways to initialize an object in Java
• C++ program to find out the number of ways a grid with boards can be colored
• Program to find sum of series 1 + 2 + 2 + 3 + 3 + 3 + .. + n in C++
• Find length of a string in python (3 ways)
• Find the Number of Ways to Traverse an N-ary Tree using C++
• Cost of painting n * m grid in C++