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| class Solution {
public:
struct morpheme
{
long digital;
char ops;
int type;
int priority = -1;
morpheme(int t, int d, char o, int p)
{
type = t;
digital = d;
ops = o;
priority = p;
}
morpheme()
{
}
};
string skipspace(string s)
{
string ans;
for (int i = 0; i < s.size(); i++) {
char c = s[i];
if (c != ' ') {
ans.push_back(c);
}
}
return ans;
}
void scanning(const string str, vector<morpheme>& v)
{
char morphemetype[] = { ')','+','-','*','/','(' };
int priority[] = { 0,1,1,3,3,5 };
int morphemetypelength = 6;
long digit = 0;
int len = str.length();
for (int i = 0; i < len; i++)
{
char c = str[i];
if (c == ' ')
{
continue;
}
bool flag = false;
for (int j = 0; j < morphemetypelength; j++)
{
if (c == morphemetype[j])
{
v.push_back(morpheme(j, 0, c, priority[j]));
flag = true;
}
}
if (flag == false)
{
digit = digit * 10 + (int)c - 0x30;
if (i == len - 1 || (str[i + 1] < '0' || str[i + 1] > '9'))
{
v.push_back(morpheme(-1, digit, '\0', -1));
digit = 0;
}
}
}
}
vector<morpheme> rpn(vector<morpheme>& v)
{
stack<morpheme> r;
stack<morpheme> opera;
for (int i = 0; i < v.size(); i++)
{
morpheme m = v[i];
if (m.type == -1)
{
r.push(m);
}
else if (m.priority == 5)
{
opera.push(m);
}
else
{
while (!opera.empty() && opera.top().priority != 5 && opera.top().priority >= m.priority)
{
r.push(opera.top());
opera.pop();
}
if (!opera.empty() && opera.top().priority == 5 && m.priority == 0)
{
opera.pop();
}
if(m.priority != 0)
{
opera.push(m);
}
}
}
while (!opera.empty())
{
r.push(opera.top());
opera.pop();
}
vector<morpheme> vv(r.size());
for (int i = r.size() - 1; i >= 0; i--)
{
vv[i] = r.top();
r.pop();
}
return vv;
}
long calcu(vector<morpheme>& rpn)
{
stack<morpheme> s;
for (int i = 0; i < rpn.size(); i++)
{
morpheme m = rpn[i];
if (m.type == -1)
{
s.push(m);
}
else
{
long left, right;
right = s.top().digital;
s.pop();
left = s.top().digital;
s.pop();
long value = 0;
if (m.type == 1)
{
value = left + right;
}
else if (m.type == 2)
{
value = left - right;
}
else if (m.type == 3)
{
value = left * right;
}
else if (m.type == 4)
{
value = left / right;
}
s.push(morpheme(-1,value,'\0',-1));
}
}
return s.top().digital;
}
int calculate(string s) {
string str = s;
str = skipspace(str);
vector<morpheme> in;
scanning(str, in);
vector<morpheme> out;
out = rpn(in);
long result = calcu(out);
return result;
}
};
|