20 Valid Parentheses

20. Valid Parentheses​
1. Question
Given a string containing just the characters'(',')','{','}','['and']', determine if the input string is valid.
The brackets must close in the correct order,"()"and"()[]{}"are all valid but"(]"and"([)]"are not.
2. Implementation
思路：查看括号匹配问题，就看相应的符号是否对称，可以直接用stack做
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class Solution {
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    public boolean isValid(String s) {
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        Stack<Character> stack = new Stack<>();
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​
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        for (char c : s.toCharArray()) {
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            if (c == '(') {
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                stack.push(')');
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            }
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            else if (c == '[') {
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                stack.push(']');
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            }
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            else if (c == '{') {
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                stack.push('}');
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            }
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            else if (stack.isEmpty() || (stack.pop() != c)) {
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                return false;
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            }
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        }
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        return stack.isEmpty();
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    }
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}
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3. Time & Space Complexity
时间和空间都是O(n)

Stack

71 Simplify Path

Last modified 2yr ago

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Contents

20. Valid Parentheses

1. Question

2. Implementation

3. Time & Space Complexity

20. Valid Parentheses​

1. Question

2. Implementation

3. Time & Space Complexity

20. Valid Parentheses