4274. Suffix expression - binary expression tree

Original link

• Postorder traversal of binary expression tree is suffix expression
• special case ： How to distinguish positive signs from plus signs in expressions , What about minus signs and minus signs ？
  answer ： If a node is “+” or “-” Number , And its left subtree is empty , Then the symbol is positive （ negative ） Number , Not plus or minus , Then the node is traversed first rather than second

ACCode

#include <bits/stdc++.h>
using namespace std;

const int N = 25;
int t[N][2], vis[N];
int n;
string v[N];

void traverse(int node)
{
    
    if (node == -1)
        return;
    if ((v[node] == "-" || v[node] == "+") && t[node][0] == -1)
    {
    
        cout << "(" << v[node];
        traverse(t[node][1]);
        cout << ")";
    }
    else
    {
    
        cout << "(";
        traverse(t[node][0]);
        traverse(t[node][1]);
        cout << v[node];
        cout << ")";
    }
}

int main()
{
    
    cin >> n;
    for (int i = 1; i <= n; i++)
    {
    
        cin >> v[i] >> t[i][0] >> t[i][1];
        if (t[i][0] != -1)
            vis[t[i][0]] = 1;
        if (t[i][1] != -1)
            vis[t[i][1]] = 1;
    }

    int p;
    for (int i = 1; i <= n; i++)
    {
    
        if (!vis[i])
        {
    
            p = i;
            break;
        }
    }
    traverse(p);
    return 0;
}