Balacing brackets
Balancing brackets = checking whether every opening bracket has a matching closing bracket in the correct order. Types usually considered: () [] {} Core idea (stack method) Use a stack : Read characters left → right. If opening bracket → push onto stack. If closing bracket → stack empty → invalid top doesn’t match → invalid else pop. End → stack must be empty. Time: O(n) Space: O(n) Example Input: {[()]} Process: { push [ push ( push ) pop ] pop } pop Stack empty → balanced. Python (clean version) def is_balanced(s): stack = [] pairs = {')': '(', ']': '[', '}': '{'} for ch in s: if ch in "([{": stack.append(ch) elif ch in ")]}": if not stack or stack[-1] != pairs[ch]: return False stack.pop() return len(stack) == 0 Edge cases people miss "(]" → order mismatch "((("...
