1557. Minimum Number of Vertices to Reach All Nodes

Given a directed acyclic graph, with n vertices numbered from 0 to n-1, and an array edges where edges[i] = [fromi, toi] represents a directed edge from node fromi to node toi.

Find the smallest set of vertices from which all nodes in the graph are reachable. It’s guaranteed that a unique solution exists.

Notice that you can return the vertices in any order.

class Solution {
public:
    vector<int> findSmallestSetOfVertices(int n, vector<vector<int>>& edges) {
        vector<bool> nodes(n);
        for(auto& e : edges) {
            nodes[e[1]] = true;
        }
        vector<int> res;
        for(int i = 0; i < n; i++)
            if(!nodes[i])
                res.push_back(i);
        return res;
    }
};