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else{
g.setColor(Color.BLACK);
g.drawString(String.valueOf(node.value), pme.x - diameter / 2, pme.y);
}
drawTree(g, node.lft, new Point(pme.x - width / 2, pme.y + levelHeight), width / 2, pme);
drawTree(g, node.rt, new Point(pme.x + width / 2, pme.y + levelHeight), width / 2, pme);
}
public TreeNode calc(String inStr) throws Exception{
opsStack.push('#');
StringBuilder buf = new StringBuilder();
int i = 0;
while(i < inStr.length()){
if(Character.isDigit(inStr.charAt(i)) || inStr.charAt(i) == '.'){// number
buf.delete(0, buf.length());
while(i < inStr.length() &&
(Character.isDigit(inStr.charAt(i)) || inStr.charAt(i) == '.'))
buf.append(inStr.charAt(i++));
Double number = Double.parseDouble(buf.toString());
nodesStack.push(new TreeNode(number));
}else if(inStr.charAt(i) == ' '){
i++;
continue;
}else{// operation
char op = inStr.charAt(i);
int subNew = getSub(op);
boolean goOn = true;
while(goOn){
if(opsStack.isEmpty())
throw new Exception("运算符太少！");
char opFormer = opsStack.peek();
int subFormer = getSub(opFormer);
switch(ops[subFormer][subNew]){
case '=':
goOn = false;
opsStack.pop();
break;
case '<':
goOn = false;
opsStack.push(op);
break;
case '>':
goOn = true;
TreeNode n1 = nodesStack.pop();
TreeNode n0 = nodesStack.pop();
double rs = doOperate(n0.value, n1.value, opFormer);
nodesStack.push(new TreeNode(rs, opFormer, n0, n1));
opsStack.pop();
break;
default:
throw new Exception("没有匹配的操作符：" + op);
}
}
i++;
}
}
return nodesStack.pop();
}
private double doOperate(double n0, double n1, char op) throws Exception{
switch(op){
case '+': return n0 + n1;
case '-': return n0 - n1;
case '*': return n0 * n1;
case '/': return n0 / n1;
default: throw new Exception("非法操作符：" + op);
}
}
private int getSub(char c){
switch(c){
case '+': return 0;
case '-': return 1;
case '*': return 2;
case '/': return 3;
case '(': return 4;
case ')': return 5;
case '#': return 6;
default : return -1;
}
}
}
class TreeNode{
public double value;
public char op = 'E';
public TreeNode lft;
public TreeNode rt;
public TreeNode(double value){
this.value = value;
}
public TreeNode(double value, char op, TreeNode lft, TreeNode rt){
this.value = value;
this.op = op;
this.lft = lft;
this.rt = rt;
}
StringBuilder buf = new StringBuilder();
public String toString(){
out(this);
return buf.toString();
}
private void out(TreeNode node){
if(node == null) return;
out(node.lft);
if(node.op != 'E')
buf.append(node.op);
else
buf.append(node.value);
out(node.rt);
}
}
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