表达式的逆波兰式转化模板

表达式的逆波兰式 ##使用方法 输入合法的表达式，加减乘除，可以带括号，例如： `a+b*(c-d)-e/f` ##模板 ``` #include #include #include #include //#include using namespace std; #define mem(x,num) memset(x,num,sizeof(x)) const int N = 1e3 + 5; const int defaultSize = 100; int lson[N], rson[N]; int nc = 0;

char op[N];
void Init() {
mem(lson, 0);
mem(rson, 0);
mem(op, 0);
nc = 0;
}
int build_Tree(char s[], int l, int r) { // Build the expression tree
int tag1 = -1, tag2 = -1, p = 0;// tag1 stand for add&sub is_exist,tag2 for muti&devide
int u;
if (r - l == 1) {// this is only one point in this interval,build it
u = ++nc;
lson[u] = rson[u] = 0;
op[u]=s[l];
return u;// return self num to fa Node
}
for (int i(l); i < r; i++) {
switch (s[i])// s[i]
{
case '(':p++; break;
case ')':p--; break;
case '+':case '-':if(!p)tag1 = i; break;// if operator in (),continue
case '*':case '/':if(!p)tag2 = i; break;
}
}
if (tag1 < 0)tag1 = tag2;// no + or - outside
if (tag1 < 0)return build_Tree(s, l + 1, r - 1); // no * or / outside mean all operator and num in ()
u = ++nc;
lson[u] = build_Tree(s, l, tag1);
rson[u] = build_Tree(s, tag1 + 1, r);
op[u] = s[tag1];
return u;
}
void Post(int rt) {// Postorder
if (lson[rt] != 0)Post(lson[rt]);
if (rson[rt] != 0)Post(rson[rt]);
cout << op[rt] << ' ';
}
int main() {
char s[defaultSize];
while (cin>>s) {
Init();
int n=0;
build_Tree(s, 0,strlen(s));
Post(1);
cout << endl;
}
return 0;
}