試了好多次都是 WA: line 103
後來把DFS換成BFS居然就AC了
所以下面的DFS函數到底哪裡寫錯了？
請大家路過幫忙看看吧

#include <cstdio>
#include <cstdlib>
#include <vector>
using namespace std;

vector < vector <int> > adj;
bool *visit;
bool *color;

bool DFS(int i) {
    for (int j = 0; j < adj[i].size(); j++) {
        if (!visit[adj[i][j]]) {
            visit[adj[i][j]] = true;
            color[adj[i][j]] = !color[i];
            DFS(adj[i][j]);
        }
        else if (color[adj[i][j]] == color[i]){
            return false;
        }
    }
    return true;
}

int main() {
    int n, m, a, b;
    adj.reserve(200);
    while (scanf("%d", &n) && n) {
        adj.resize(n);
        visit = (bool *)calloc(n, sizeof(bool));
        color = (bool *)calloc(n, sizeof(bool));
        scanf("%d", &m);
        for (int i = 0; i < m; i++) {
            scanf("%d %d", &a, &b);
            adj[a].push_back(b);
            adj[b].push_back(a);
        }
        visit[0] = true;
        color[0] = true;
        if (DFS(0))
            printf("BICOLORABLE.\n");
        else
            printf("NOT BICOLORABLE.\n");
        adj.clear();
        free(visit);
        free(color);
    }
    return (0);
}