LeetCode 785 Is Graph Bipartite? - Conflict Example

let's trace a triangle: graph = [[1,2],[0,2],[0,1]]. Start: color = [-1,-1,-1]. BFS from $0$. Color $0$ as $0$. Queue: [0]. Pop $0$. Neighbors: $1$, $2$. Color $1$ as $1$, color $2$ as $1$. Queue: [1, 2]. Pop $1$. Neighbors: $0$, $2$.

Node $0$ has color $0$ (opposite of $1$, good). Node $2$ has color $1$ (same as $1$). Conflict! Return false. The triangle is an odd cycle. You caught it the moment two neighbors tried to have the same color.