二分图的算法

1.染色法判断二分图

785. 判断二分图

class Solution {
    int[] color;
    int[][] g;
    
    public boolean dfs(int i, int v){
        color[i]=v;
        for (int node: g[i]){
            if (color[node]==0){
                if(!dfs(node,3-v))  return false;
            }
            else if (color[node]==v)    return false;
        }
        return true;
    }

    public boolean isBipartite(int[][] graph) {
        //染色法判断二分图
        this.g = graph;
        int n=graph.length;
        color = new int[n];

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