队列

用队列（queue）解答可能会比较麻烦点，但还好理解

#include <bits/stdc++.h>
using namespace std;
int n;
int t[5005];
queue<int> qu1;
queue<int> qu2;
queue<int> qu3;
int main() {
    cin >> n;
    for (int i = 1;i <= n;i++) {
        cin >> t[i];
        if (t[i] == 1) {
            qu1.push(i);
        } else if (t[i] == 2) {
            qu2.push(i);
        } else if (t[i] == 3) {
            qu3.push(i);
        }
    }
    int min_ans = min(qu1.size(), min(qu2.size(), qu3.size()));
    cout << min_ans << endl;
    if (min_ans != 0) {
        for (int i = 1;i <= min_ans;i++) {
            cout << qu1.front() << " " << qu2.front() << " " << qu3.front() << endl;
            qu1.pop();
            qu2.pop();
            qu3.pop();
        }
    }
        
    return 0;
}