Valid Matrix Color Pattern

Given a matrix representing colors where each color is represented by an integer, determine if the following rule holds: No two adjacent cells (horizontally or vertically) can have the same color. Input format: The first line contains two integers, N (the number of rows) and M (the number of columns). The next N lines contain M integers each, indicating colors. Output format: Print 'YES' if the matrix holds the rule, otherwise print 'NO'. Example: Input: 3 3 1 2 1 2 1 2 1 2 1 Output: YES