19 May Find k-th smallest element in given n ranges

class Solution {
public:
    bool isBipartite(vector<vector<int>>& graph) {
        int n = graph.size();
        vector<int> colors(n, 0);

        for (int i = 0; i < n; i++) {
            if (colors[i] == 0 && !dfs(graph, colors, i, 1)) {
                return false;
            }
        }

        return true;
    }

private:
    bool dfs(vector<vector<int>>& graph, vector<int>& colors, int node, int color) {
        if (colors[node] != 0) {
            return colors[node] == color;
        }

        colors[node] = color;

        for (int neighbor : graph[node]) {
            if (!dfs(graph, colors, neighbor, -color)) {
                return false;
            }
        }

        return true;
    }
};