题目

题目链接：
https://www.nowcoder.com/practice/37548e94a270412c8b9fb85643c8ccc2

核心

 栈的思想

参考答案C++

class Solution {public:/*** 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可*** @param s string字符串* @return bool布尔型*/bool isValid(string s) {//本答案用vector模拟栈vector<char> stack(s.size());int idx = 0;for (int i = 0; i < s.size(); i++) {char c = s[i];if (c == '(' || c == '[' || c == '{') {stack[idx++] = c;} else {char pop = '1';if (idx > 0) {pop = stack[--idx];}if (c == ')' && pop != '(') return false;if (c == ']' && pop != '[') return false;if (c == '}' && pop != '{') return false;}}if (idx > 0) return false;return true;}
};

参考答案Java

import java.util.*;public class Solution {/*** 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可*** @param s string字符串* @return bool布尔型*/public boolean isValid (String s) {//栈,本答案用数组模拟栈//Stack<Character> stack = new Stack<>();char[] arr = new char[s.length()];int idx = 0;for (int i = 0; i < s.length(); i++) {char c = s.charAt(i);if (c == '(' || c == '[' || c == '{') {//stack.add(c);arr[idx++] = c;} else {//char pop = stack.pop();char pop = idx>0 ? arr[--idx]:'1';if (c == ')' && pop != '(') return false;if (c == ']' && pop != '[') return false;if (c == '}' && pop != '{') return false;}}//if(stack.size()>0) return false;if (idx > 0) return false;return true;}
}

参考答案Go

package main/*** 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可*** @param s string字符串* @return bool布尔型*/
func isValid(s string) bool {//栈，本答案用切片模拟栈stack := make([]byte, len(s))idx := 0for i := 0; i < len(s); i++ {c := s[i]if c == '(' || c == '[' || c == '{' {stack[idx] = cidx++} else {var pop byte = '1'if idx > 0 {idx -= 1pop = stack[idx]}if c == ')' && pop != '(' {return false}if c == ']' && pop != '[' {return false}if c == '}' && pop != '{' {return false}}}if idx > 0 {return false}return true
}

参考答案PHP

<?php/*** 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可** * @param s string字符串 * @return bool布尔型*/
function isValid( $s )
{//本答案用数组模拟栈$stack = [];$idx=0;for($i=0;$i<strlen($s);$i++){$c = $s[$i];if($c=='(' || $c =='[' || $c =='{'){$stack[$idx++] = $c;}else{$pop = '1';if($idx>0){$idx--;$pop=$stack[$idx];}if($c ==')' && $pop!='(') return false;if($c ==']' && $pop!='[') return false;if($c =='}' && $pop!='{') return false;}}if($idx >0) return false;return true;
}