#include <iostream>

#include <vector>
#include <unordered_set>

using namespace std;
 bool isValidSudoku(vector<vector<char>>& board) {
      
	// Create vectors of unordered sets to keep track of numbers in rows, columns, and boxes
	vector<unordered_set<int>> rows(9);
	vector<unordered_set<int>> columns(9);
	vector<unordered_set<int>> boxes(9);

	// Iterate through each cell in the Sudoku board
	for (int i = 0; i < 9; i++) {
		for (int j = 0; j < 9; j++) {
			// If the cell is empty, continue to the next cell
			int index = (i / 3) * 3 + j / 3;
			if (board[i][j] == '.') {
				
				  
				  continue;
			}

			// Convert the character to an integer to get the number in the cell
			int num = board[i][j] - '0';

			// Check if the same number already exists in the current row
			if (rows[i].count(num)) {
				return false; // If yes, the Sudoku is invalid
			}

			// Check if the same number already exists in the current column
			if (columns[j].count(num)) {
				return false; // If yes, the Sudoku is invalid
			}

			// Calculate the index of the box the current cell belongs to
			

			// Check if the same number already exists in the current box
			if (boxes[index].count(num)) {
				return false; // If yes, the Sudoku is invalid
			}

			// If the number doesn't violate any rules, insert it into the sets
			rows[i].insert(num);
			columns[j].insert(num);
			boxes[index].insert(num);
		}
	}
return true;
}
int main() 
{
  vector<vector<char>> A = {
  {'5','3','.','.','7','.','.','.','.'},
  {'6','.','.','1','9','5','.','.','.'}, 
  {'.','9','8','.','.','.','.','6','.'}, 
  {'8','.','.','.','6','.','.','.','3'}, 
  {'4','.','.','8','.','3','.','.','1'}, 
  {'7','.','.','.','2','.','.','.','6'}, 
  {'.','6','.','.','.','.','2','8','.'}, 
  {'.','.','.','4','1','9','.','.','5'},
  {'.','.','.','.','8','.','.','7','9'}};
  
 bool result =  isValidSudoku(A);
 cout << result<<endl;
 
 
 for (int i = 0; i < 9; i++) {
		for (int j = 0; j < 9; j++) {
		
   	if (A[i][j] == '.') {
   	      int k = 1;
			    A[i][j] = k + '0';
				  while(isValidSudoku(A) == 0)
				  {  
				      k++;
				    
    				 A[i][j] = k + '0';
				  
				      
				  }
				  
				
			}
	
}
   
 }
 
 
 
  for(int i = 0; i<9; i++) {
for(int j = 0; j<9; j++) {
cout << "  "  << A[i][j] << "  "  ;
}
cout << "\n";
}
 
 }

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Read inputs from stdin

OneCompiler's C++ online compiler supports stdin and users can give inputs to programs using the STDIN textbox under the I/O tab. Following is a sample program which takes name as input and print your name with hello.

#include <iostream>
#include <string>
using namespace std;

int main() 
{
    string name;
    cout << "Enter name:";
    getline (cin, name);
    cout << "Hello " << name;
    return 0;
}

About C++

C++ is a widely used middle-level programming language.

  • Supports different platforms like Windows, various Linux flavours, MacOS etc
  • C++ supports OOPS concepts like Inheritance, Polymorphism, Encapsulation and Abstraction.
  • Case-sensitive
  • C++ is a compiler based language
  • C++ supports structured programming language
  • C++ provides alot of inbuilt functions and also supports dynamic memory allocation.
  • Like C, C++ also allows you to play with memory using Pointers.

Syntax help

Loops

1. If-Else:

When ever you want to perform a set of operations based on a condition If-Else is used.

if(conditional-expression) {
   //code
}
else {
   //code
}

You can also use if-else for nested Ifs and If-Else-If ladder when multiple conditions are to be performed on a single variable.

2. Switch:

Switch is an alternative to If-Else-If ladder.

switch(conditional-expression){    
case value1:    
 // code    
 break;  // optional  
case value2:    
 // code    
 break;  // optional  
......    
    
default:     
 code to be executed when all the above cases are not matched;    
}

3. For:

For loop is used to iterate a set of statements based on a condition.

for(Initialization; Condition; Increment/decrement){  
  //code  
}

4. While:

While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.

while (condition) {  
// code 
}

5. Do-While:

Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.

do {  
 // code 
} while (condition);

Functions

Function is a sub-routine which contains set of statements. Usually functions are written when multiple calls are required to same set of statements which increases re-usuability and modularity. Function gets run only when it is called.

How to declare a Function:

return_type function_name(parameters);

How to call a Function:

function_name (parameters)

How to define a Function:

return_type function_name(parameters) {  
 // code
}