yukicoder No.323 yuki国
解法
done[size][y][x] = (雪玉の大きさが size で, 座標が (y, x) にあるような場合があるか) というのを, 幅優先探索すれば良いです。
struct State { int size; int y; int x; State() {} State(int size, int y, int x) : size(size), y(y), x(x) {} }; bool done[2000][55][55]; string field[55]; int main() { cin.tie(0); ios::sync_with_stdio(false); int H, W; cin >> H >> W; int A, Si, Sj; cin >> A >> Si >> Sj; int B, Gi, Gj; cin >> B >> Gi >> Gj; for (int i = 0; i < H; i++) cin >> field[i]; queue<State> que; que.push(State(A, Si, Sj)); done[A][Si][Sj] = true; while (!que.empty()) { State s = que.front(); que.pop(); for (int k = 0; k < 4; k++) { int ny = s.y+dy[k]; int nx = s.x+dx[k]; if (ny < 0 || ny >= H || nx < 0 || nx >= W) continue; int nsize = s.size; if (field[ny][nx] == '*') nsize++; else nsize--; if (nsize <= 0 || nsize >= 2000) continue; if (done[nsize][ny][nx]) continue; done[nsize][ny][nx] = true; que.push(State(nsize, ny, nx)); } } if (done[B][Gi][Gj]) cout << "Yes" << endl; else cout << "No" << endl; return 0; }