invalid type int[int] for array subscript

Question

This is my code.

#include<bits/stdc++.h>

using namespace std;

#define IOS ios::sync_with_stdio(0);cin.tie(0);
#define pb push_back;
#define rep(i,j,k) for(int i = j;i < k; i++)

vector<int> r;
bool bad[10006];

bool track(int y){
    if(bad[y]) return 1;
    rep(i,0,(int)r[y].size()){
        if(track(r[y][i])) return 1;
    }
    return 0;
}

int main(){
    IOS
    int n,m,l,q;
    cin >> n >> m >> l >> q;
    rep(i,0,m){
        int a,b; cin >> a >> b;
        r[b].pb(a);
    }
    rep(i,0,l){
        int x; cin >> x;
        bad[x] = 1;
    }
    rep(i,0,q){
        int y; cin >> y;
        if(track(y)){
            cout << "TUIHUOOOOOO\n";
        }
        else{
            cout << "YA~~\n";
        }
    }
    return 0;
}

Dev c++ kept saying that rep(i,0,(int)r[y].size()) has invalid type int[int]. I don't understand why this is invalid. I have searched for this problem but don't get any answer. The problem I only think of is that I used the same name to announce different data type, but I think I don't make this mistake.

If in doubt, expand your code with `g++ -E` to see what you macro magic results in. There is a reason that such macro stuff is considered as bad style (ignoring the general problems of macros in C++). — Scheff's Cat, Aug 25 '19 at 08:56
Try to change `rep(i,0,(int)r[y].size())` to `rep(i,0,(int)r.size())`. — andresantacruz, Aug 25 '19 at 08:57
john said it all. almost. Also , don't use `#include` (And if you use, `using namespace ` is already in it) That bits directory is just that: naughty bits of tool chain, no decent program would touch it. — Swift - Friday Pie, Aug 25 '19 at 09:04
@Swift-FridayPie Here's the obligatory link: https://stackoverflow.com/questions/31816095/why-should-i-not-include-bits-stdc-h — πάντα ῥεῖ, Aug 25 '19 at 09:30

john · Answer 1 · 2019-08-25T09:20:32.230

In r[y].size(), r is a vector<int>, so r[y] is an int. There is no method called size that can be called on an int (or in fact any method at all). That's explains the error.

Your code is treating r as if it is a two dimensional vector/array, but it isn't. So vector<vector<int>> r; would help, but your code has other problems as you'll find out when you run it.

And please stop using those macros. Apart from being badly written, they also obscure your code. If you were in my class and you handed that it, I would fail you. I really hope you haven't been told that you must use them.

invalid type int[int] for array subscript

1 Answers1