Clear Cut Two-Pointer Solution in Python
Intuition\nThe problem requires us to determine if we can transform the string start into target using valid moves for the pieces $L$ and $R$.\n\n# Approach\nKe
# Intuition\nThe problem requires us to determine if we can transform the string start into target using valid moves for the pieces $L$ and $R$.\n\n# Approach\n<B>Key Observations:</B>\n1. <I>Character Equality:</I> The sequence of non-underscore characters (\'L\' and \'R\') in start and target must match, preserving their relative order. If start.replace(\'_\', \'\') != target.replace(\'_\', \'\'), the transformation is impossible.\n\n<B>Movement Rules:</B>\n\n1. An \'L\' can only move to the left, so it must not cross an \'R\' or be found further to the right than its corresponding position in target.\n2. An \'R\' can only move to the right, so it must not cross an \'L\' or be found further to the left than its corresponding position in target.\nEfficient Validation: Instead of simulating the moves, we can check if all movement constraints hold by comparing indices.\n\n<B>Plan:</B>\n1. Compare start and target after removing underscores to ensure the characters match.\n2. Use two pointers to validate the movement constraints for each \'L\' and \'R\'.\n\n\n# Complexity\n- Time complexity: $O(N)$\n<!-- Add your time complexity here, e.g. $$O(n)$$ -->\n\n- Space complexity: $O(1)$\n<!-- Add your space complexity here, e.g. $$O(n)$$ -->\n\n# Code\n```python3 []\nclass Solution:\n    def canChange(self, start: str, target: str) -> bool:\n        # Step 1: Remove underscores and check if the character sequence matches\n        if start.replace(\'_\', \'\') != target.replace(\'_\', \'\'):\n            return False\n\n        n = len(start)\n        i, j = 0, 0\n\n        # Step 2: Use two pointers to check movement constraints\n        while i < n and j < n:\n            # Skip underscores in start\n            while i < n and start[i] == \'_\':\n                i += 1\n            # Skip underscores in target\n            while j < n and target[j] == \'_\':\n                j += 1\n\n            # If both pointers are out of bounds, we\'re done\n            if i == n and j == n:\n                return True\n            # If one pointer is out of bounds but not the other, return False\n            if i == n or j == n:\n                return False\n\n            # Check movement constraints for \'L\' and \'R\'\n            if start[i] != target[j]:\n                return False\n            if start[i] == \'L\' and i < j:  # \'L\' cannot move to the right\n                return False\n            if start[i] == \'R\' and i > j:  # \'R\' cannot move to the left\n                return False\n\n            # Move both pointers\n            i += 1\n            j += 1\n\n        return True\n\n```
['Two Pointers', 'String', 'Python', 'Python3']