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出处 LeetCode 算法第150题 逆波兰表达式求值 根据逆波兰表示法,求表达式的值。 有效的运算符包括 +, -, *, / 。每个运算对象可以是整数,也可以是另一个逆波兰表达式。 说明: 整数除法只保留整数部分。 给定逆波兰表达式总是有效的。换句话说,表达式总会得出有效数值且不存在除数为 0 的情况。 示例 1: 输入: ["2", "1", "+", "3", "*"] 输出: 9 解释: ((2 + 1) * 3) = 9 示例 2: 输入: ["4", "13", "5", "/", "+"] 输出: 6 解释: (4 + (13 / 5)) = 6 示例 3: 输入: ["10", "6", "9", "3", "+", "-11", "*", "/", "*", "17", "+", "5", "+"] 输出: 22 解释: ((10 * (6 / ((9 + 3) * -11))) + 17) + 5 = ((10 * (6 / (12 * -11))) + 17) + 5 = ((10 * (6 / -132)) + 17) + 5 = ((10 * 0) + 17) + 5 = (0 + 17) + 5 = 17 + 5 = 22
出处 LeetCode 算法第150题
逆波兰表达式求值
根据逆波兰表示法,求表达式的值。
有效的运算符包括 +, -, *, / 。每个运算对象可以是整数,也可以是另一个逆波兰表达式。
+
-
*
/
说明:
示例 1:
输入: ["2", "1", "+", "3", "*"] 输出: 9 解释: ((2 + 1) * 3) = 9
示例 2:
输入: ["4", "13", "5", "/", "+"] 输出: 6 解释: (4 + (13 / 5)) = 6
示例 3:
输入: ["10", "6", "9", "3", "+", "-11", "*", "/", "*", "17", "+", "5", "+"] 输出: 22 解释: ((10 * (6 / ((9 + 3) * -11))) + 17) + 5 = ((10 * (6 / (12 * -11))) + 17) + 5 = ((10 * (6 / -132)) + 17) + 5 = ((10 * 0) + 17) + 5 = (0 + 17) + 5 = 17 + 5 = 22
使用堆栈可以很轻易的解决问题
var evalRPN = function (tokens) { var stack = []; var result = 0; tokens.forEach(function (item) { if (isOperator(item)) { var operate1 = stack.pop(); var operate2 = stack.pop(); switch (item) { case '+': result = Number(operate1) + Number(operate2); break; case '-': result = Number(operate2) - Number(operate1); break; case '*': result = Number(operate2) * Number(operate1); break; case '/': result = Number(operate2) / Number(operate1) > 0 ? Math.floor(Number(operate2) / Number(operate1)) : Math.ceil(Number(operate2) / Number(operate1)); break; } stack.push(result); } else { stack.push(item); } }) return stack.pop(); }; function isOperator(value) { if (['+', '-', '*', '/'].indexOf(value) >= 0) { return true } return false; }
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习题
思路
使用堆栈可以很轻易的解决问题
解答
The text was updated successfully, but these errors were encountered: