```cpp
if(ex[i]>='0'&&ex[i]<='9')
num.push(var[ex[i]-'0']);
```
这句是错的，x之后可能有多位，应该改成
```cpp
if(ex[i]=='x')
{
i++;
int x=0;
while(ex[i]>='0'&&ex[i]<='9')
x=x*10+(ex[i]-'0'),i++;
num.push(var[x]);
}
```
by like_rain @ 2022-01-28 17:32:14