Code Editor for app.py

import streamlit as st
import numpy as np

def solve_sudoku(board):
    empty = find_empty(board)
    if not empty:
        return True  # Solved
    row, col = empty
    for num in range(1, 10):  # Numbers 1-9
        if is_valid(board, num, row, col):
            board[row][col] = num  # Place number
            if solve_sudoku(board):
                return True
            board[row][col] = 0  # Reset on backtrack
    return False

def find_empty(board):
    for r in range(len(board)):
        for c in range(len(board[0])):
            if board[r][c] == 0:
                return (r, c)  # Row, Col
    return None

def is_valid(board, num, row, col):
    # Check row
    if num in board[row]:
        return False
    # Check column
    if num in [board[r][col] for r in range(len(board))]:
        return False
    # Check box
    box_row_start = (row // 3) * 3
    box_col_start = (col // 3) * 3
    for r in range(box_row_start, box_row_start + 3):
        for c in range(box_col_start, box_col_start + 3):
            if board[r][c] == num:
                return False
    return True

st.title("Sudoku Solver")

size = st.sidebar.number_input("Select the size of the Sudoku (3 for 9x9)", min_value=1, max_value=3, value=1)

n = size * 3
board = np.zeros((n, n), dtype=int)

for i in range(n):
    row = st.text_input(f"Row {i + 1} (comma separated)", "").split(',')
    board[i] = [int(num) if num.strip() else 0 for num in row]

if st.button("Solve Sudoku"):
    if solve_sudoku(board):
        st.success("Solved Sudoku:")
        st.table(board)
    else:
        st.error("No solution exists.")