求助，使用getchar评测结果与本地运行不一致？？

读取部分：

正确

    cin >> n;
    // getchar();
    string s;
    for (int i = 1; i <= n; ++i)
        for (int j = 1; j <= n; ++j)
        {
            cin >> s;
            g[i][j] = s[0];
            if (s == "A")
                sx = i, sy = j;
            if (s == "B")
                ex = i, ey = j;
        }

错误 getchar

本地运行结果正确，评测机只有一个测试点AC

    for (int i = 1; i <= n; ++i)
    {
        for (int j = 2; j <= n * 2 + 1; ++j)
        {
            char ch = getchar();
            if (ch == 'A')
                sx = i, sy = j / 2;
            if (ch == 'B')
                ex = i, ey = j / 2;
            if (j % 2 == 0)
                g[i][j / 2] = ch;
        }
        getchar();
    }

完整代码

// P1649 [USACO07OCT] Obstacle Course S
// BFS

#include <iostream>
#include <cstdio>
#include <cstring>
#include <queue>
#include <algorithm>
using namespace std;

const int maxn = 110;
struct Node
{
    int x, y, dr;
};
char g[maxn][maxn];
int n, sx, sy, ex, ey, ans = 0x3f3f3f3f;
int turn[maxn][maxn][4];
int dx[] = {-1, 0, 1, 0}, dy[] = {0, 1, 0, -1}; // 上右下左 0123

int bfs()
{
    memset(turn, 0x3f, sizeof turn);
    queue<Node> q;
    for (int i = 0; i < 4; ++i)
    {
        q.push({sx, sy, i});
        turn[sx][sy][i] = 0;
    }

    while (!q.empty())
    {
        auto t = q.front();
        q.pop();
        if (turn[t.x][t.y][t.dr] > ans)
            continue;

        for (int i = 0; i < 4; ++i)
        {
            int xx = t.x + dx[i], yy = t.y + dy[i];
            if (xx < 1 || xx > n || yy < 1 || yy > n || g[xx][yy] == 'x')
                continue;
            if (xx == ex && yy == ey)
                ans = min(ans, turn[xx][yy][i] + (t.dr == i ? 0 : 1));
            if (turn[xx][yy][i] == 0x3f3f3f3f)
            {
                turn[xx][yy][i] = turn[t.x][t.y][t.dr] + (t.dr == i ? 0 : 1);
                q.push({xx, yy, i});
            }
            else if (turn[xx][yy][i] > turn[t.x][t.y][t.dr] + (t.dr == i ? 0 : 1)) // 允许重复走到同一位置(来的方向不同)
                turn[xx][yy][i] = turn[t.x][t.y][t.dr] + (t.dr == i ? 0 : 1);
        }
    }

    int res = 0x3f3f3f3f;
    for (int i = 0; i < 4; ++i)
        res = min(turn[ex][ey][i], res);

    return res == 0x3f3f3f3f ? -1 : res;
}

int main()
{
    cin >> n;
    // getchar();
    string s;
    for (int i = 1; i <= n; ++i)
        for (int j = 1; j <= n; ++j)
        {
            cin >> s;
            g[i][j] = s[0];
            if (s == "A")
                sx = i, sy = j;
            if (s == "B")
                ex = i, ey = j;
        }

    // for (int i = 1; i <= n; ++i)
    // {
    //     for (int j = 2; j <= n * 2 + 1; ++j)
    //     {
    //         char ch = getchar();
    //         if (ch == 'A')
    //             sx = i, sy = j / 2;
    //         if (ch == 'B')
    //             ex = i, ey = j / 2;
    //         if (j % 2 == 0)
    //             g[i][j / 2] = ch;
    //     }
    //     getchar();
    // }
    // for (int i = 1; i <= n; ++i)
    //     printf("%s\n", g[i] + 1);
    // cout << sx << " " << sy << endl;
    // cout << ex << " " << ey << endl;
    cout << bfs();

    return 0;
}