问题描述如下:
Evaluate the value of an arithmetic expression in Reverse Polish Notation.
Valid operators are +
, -
, *
, /
. Each operand may be an integer or another expression.
Some examples:
["2", "1", "+", "3", "*"] -> ((2 + 1) * 3) -> 9 ["4", "13", "5", "/", "+"] -> (4 + (13 / 5)) -> 6问题链接
cpp代码如下:
class Solution {
public:
int evalRPN(vector<string> &tokens) {
stack<int> nums;
int size_=tokens.size();
int n1=0,n2=0;
for(int i=0;i<size_;++i){
if(tokens[i].length()==1){
switch(tokens[i][0]){
case '+':
case '-':
case '*':
case '/':
n1=nums.top();
nums.pop();
n2=nums.top();
nums.pop();
switch(tokens[i][0]){
case '+':
nums.push(n2+n1);break;
case '-':
nums.push(n2-n1);break;
case '*':
nums.push(n2*n1);break;
case '/':
nums.push(n2/n1);break;
}
continue;
}
}
int n=0;
bool neg=false;
unsigned int j=0;
if(tokens[i][0]=='-'){
neg=true;
j=1;
}
for(;j<tokens[i].length();++j){
n*=10;
n+=tokens[i][j]-'0';
}
if(neg)n*=-1;
nums.push(n);
}
return nums.top();
}
};