function solve() {
  let rows = document
    .getElementsByTagName('tbody')[0]
    .getElementsByTagName('tr');
  let buttons = document.getElementsByTagName('button');

  let checkBtn = buttons[0];
  let clearBtn = buttons[1];

  checkBtn.addEventListener('click', () => {
    let inputs = Array.from(document.getElementsByTagName('input'));

    let emptyOrWrongInput = checkIfInputsEmptyOrWrong(inputs);

    if (emptyOrWrongInput) {
      outputNotSolved();
      return;
    }

    let rowsSame = checkRows(inputs);
    let colsSame = checkCols(inputs);

    if (rowsSame || colsSame) {
      outputNotSolved();
    } else {
      outputSolved();
    }
  });

  clearBtn.addEventListener('click', () => {
    for (const row of rows) {
      Array.from(row.children).forEach((el) => {
        el.children[0].value = '';
      });
    }
    document.getElementsByTagName('table')[0].style.border = '';
    document.getElementById('check').children[0].textContent = '';
  });

  function outputNotSolved() {
    document.getElementsByTagName('table')[0].style.border = '2px solid red';
    document.getElementById('check').children[0].textContent =
      'NOP! You are not done yet...';
  }

  function outputSolved() {
    document.getElementsByTagName('table')[0].style.border = '2px solid green';
    document.getElementById('check').children[0].textContent =
      'You solve it! Congratulations!';
  }

  function checkIfInputsEmptyOrWrong(inputs) {
    for (const input of inputs) {
      if (input.value === '') {
        return true;
      }
      let number = +input.value;
      if (number < 1 || number > 3) {
        return true;
      }
    }
    return false;
  }

  function checkRows(inputs) {
    for (let i = 0; i < inputs.length; i += 3) {
      for (let j = i + 1; j < i + 3; j++) {
        if ((j + 1) % 3 === 0) {
          if (inputs[j - 1].value === inputs[j].value) {
            return true;
          }
        }
        if (inputs[i].value === inputs[j].value) {
          return true;
        }
      }
    }
    return false;
  }

  function checkCols(inputs) {
    for (let i = 0; i < inputs.length / 3; i++) {
      for (let j = i + 3; j < inputs.length; j += 3) {
        if (j >= inputs.length - 3) {
          if (inputs[j - 3].value === inputs[j].value) {
            return true;
          }
        }
        if (inputs[i].value === inputs[j].value) {
          return true;
        }
      }
    }
    return false;
  }
}