Basic Calculator II
阿新 • • 發佈：2017-06-19
運算 全部 bstr als ont sub stack substr 元素
該題和前面的"
Basic Calculator
"的處理方法一樣，僅僅是增加了對"*"、"/"兩種運算的支持。class Solution {
public:
bool isnum(char c){
if(c >= '0' && c <= '9')
return true;
return false;
}
int calculate(string s) {
vector<string> postorder;
stack<char> ccache;
stack<int> icache;
string tmp;
if(s.length() < 1)
return 0;
//構造後綴表達式
for(int i = 0; i < s.length(); ){
if(s[i] == ' '){
i++;
continue;
}
if(!isnum(s[i])){
if(s[i] == '(' || ccache.empty()){
ccache.push(s[i]);
i++;
continue;
}
if(s[i] == ')'){
while(ccache.top() != '('){
tmp = "";
tmp += ccache.top();
postorder.push_back(tmp);
ccache.pop();
}
ccache.pop();
i++;
continue;
}
if(s[i] == '+' || s[i] == '-'){
while(!ccache.empty() && ccache.top() != '(' ){
tmp = "";
tmp += ccache.top();
postorder.push_back(tmp);
ccache.pop();
}
ccache.push(s[i]);
i++;
continue;
}
if(s[i] == '*' || s[i] == '/'){
while(!ccache.empty() && ccache.top() != '(' && ccache.top() != '+' && ccache.top() != '-'){
tmp = "";
tmp += ccache.top();
postorder.push_back(tmp);
ccache.pop();
}
ccache.push(s[i]);
i++;
continue;
}
}else{
int j = i;
while(j < s.length() && isnum(s[j]))
j++;
tmp = "";
tmp = s.substr(i, j - i);
postorder.push_back(tmp);
i = j;
}
}
//加入全部剩余的元素
while(!ccache.empty()){
tmp = "";
tmp += ccache.top();
ccache.pop();
postorder.push_back(tmp);
}
//通過後綴表達式計算結果值
int fir, sec, result;
for(int i = 0; i < postorder.size(); i++){
if(postorder[i] == "+" || postorder[i] == "-" || postorder[i] == "*" || postorder[i] == "/"){
sec = icache.top();
icache.pop();
fir = icache.top();
icache.pop();
if(postorder[i] == "+")
result = fir + sec;
if(postorder[i] == "-")
result = fir - sec;
if(postorder[i] == "*")
result = fir * sec;
if(postorder[i] == "/")
result = fir / sec;
icache.push(result);
}else{
icache.push(atoi(postorder[i].c_str()));
}
}
return icache.top();
}
};Basic Calculator II