LeetCode[20] Valid Parentheses

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.

分析:

使用栈。

代码:

public class Solution {
public boolean isValid(String s) {
Stack<Character> stack = new Stack<Character>();
for (char c : s.toCharArray()) {
if (c == '(') {
stack.push(')');
} else if (c == '[') {
stack.push(']');
} else if (c == '{') {
stack.push('}');
} else if (stack.isEmpty() || stack.pop() != c) {
return false;
}
}
return stack.isEmpty();
}
}

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