BFS taking twice the distance in undirected graph

could you help me out with this code(I got it from github because it's clear and follow the same logic that I do, also the same problem,I just added some details like predecessors that I'm using)? Well, I tried a lot of times but I couldn't figure out the problem, I don't understand why my bfs algorithm (and this one) the wrong distance in an undirected and weighted graph consider my graph is using matrix, but when I use bfs to travel from b to c, for example, I got 5 and not just 2 as the cost... and a to b I got 2, what is the right answer. a b c d a | 0 2 0 0 b | 2 0 0 3 c | 0 0 0 0 d | 0 3 0 0 Here is the code: const int branco = 0; const int cinza = 1; const int preto = 2; int bfs(int start, int target) { int color[countVertices]; queue<int> fila; dist = 0; predecessors.clear(); for (int i = 0; i < countVertices; i++) { color[i] = white; } color[start] = grey; fila.push(start); while (!fila.empty()) { int u = fila.front(); fila.pop(); if (u == target) return 1; for (int v = 0; v < countVertices; v++) { if (matriz[u][v] != 0 && color[v] == white) { color[v] = grey; fila.push(v); dist += matriz[u][v]; // sum weight predecessors.push_front(u); // predecessor } } color[u] = black; } return 0; }