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53 | public class Solution {
public int calculate(String s) {
s = s.replaceAll(" ", "");
List<String> list = new LinkedList<String>();
String prev = "";
int i = 0;
while(i<s.length()){
char current = s.charAt(i);
if (current == '*' || current == '/'){
int numberEnd = nextNumberRange(s, i+1);
int op2 = Integer.valueOf(s.substring(i+1, numberEnd));
list.add(doMath(current, Integer.valueOf(list.remove(list.size()-1)), op2)+"");
i = numberEnd;
}else if (current == '+' || current == '-'){
list.add(current+"");
i++;
}else{
int numberEnd = nextNumberRange(s, i);
list.add(s.substring(i, numberEnd));
i = numberEnd;
}
}
if (list.isEmpty()) return 0;
while (list.size()!=1){
int op1 = Integer.valueOf(list.remove(0));
char op = list.remove(0).charAt(0);
int op2 = Integer.valueOf(list.remove(0));
list.add(0,doMath(op, op1, op2)+"");
}
return Integer.valueOf(list.remove(0));
}
private int doMath(char op, int op1, int op2){
if (op == '*') return op1*op2;
if (op == '/') return op1/op2;
if (op == '-') return op1-op2;
return op1+op2;
}
private int nextNumberRange(String s, int starting){
while (starting < s.length()){
char current = s.charAt(starting);
if (current == '*' || current == '/'
||current == '-' || current == '+'){
return starting;
}
starting++;
}
return starting;
}
}
|
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