0227-basic-calculator-ii.adoc

227. Basic Calculator II

{leetcode}/problems/basic-calculator-ii/[LeetCode - Basic Calculator II^]

这里在处理将字符串转成数字时，从左向右按位乘以十再相加的方法，这样就可以只遍历一遍字符串。

另外，这里还有个地方需要注意：在确定当前操作符的情况下，再计算上一次的值。所以，就需要把上一次的值保存下来。

思考题：如果数字是全体整数，又该如何实现？如果再扩容成实数呢？

Implement a basic calculator to evaluate a simple expression string.

The expression string contains only non-negative integers, +, -, *, / operators and empty spaces ` `. The integer division should truncate toward zero.

Example 1:

Input: "3+2*2"
Output: 7

Example 2:

Input: " 3/2 "
Output: 1

Example 3:

Input: " 3+5 / 2 "
Output: 5

Note:

• You may assume that the given expression is always valid.

• Do not use the eval built-in library function.

link:{sourcedir}/_0227_BasicCalculatorIi.java[role=include]