题目
添加链接描述
解题思路
- 从前向后遍历数组
- 遇到数字则压入栈中
- 遇见计算符则将栈顶的前两个字符进行运算,结果再加入栈中
- 遍历数组到最后,栈顶元素即为最后答案
public class Solution {
public int EvalRPN(string[] tokens) {
Stack<int> data = new Stack<int>();
for (int i = 0; i < tokens.Length; i++)
{
if (tokens[i] == "+" || tokens[i] == "/" || tokens[i] == "-" || tokens[i] == "*")
{
int a = data.Pop();
int b = data.Pop();
if (tokens[i] == "+")
{
data.Push(b + a);
}
if (tokens[i] == "-")
{
data.Push(b - a);
}
if (tokens[i] == "*")
{
data.Push(b * a);
}
if (tokens[i] == "/")
{
data.Push(b / a);
}
}
else
data.Push(int.Parse(tokens[i]));
}
return data.Pop();
}
}