Lưu ý: Các code mẫu dưới đây chỉ mang tính tham khảo và có thể không AC được bài tập này

Code mẫu của flashmt

#include <iostream>
#include <algorithm>
#include <string>
#define sqr(x) (x)*(x)
using namespace std;
const int dx[]={-1,0,1,0};
const int dy[]={0,1,0,-1};

int m,n,k,step,ans,f[100][100],d[100][100],a[100][100];
int qx[100][3000],qy[100][3000],Q[100];

void push(int z,int x,int y)
{
    qx[z][++Q[z]]=x; qy[z][Q[z]]=y;
    d[x][y]=step;
}

void visit(int sx,int sy)
{
    if (a[sx][sy]>k) return;
    for (int F=0;F<100;F++) Q[F]=0;
    ++step;
    f[sx][sy]=a[sx][sy];
    push(f[sx][sy],sx,sy);
    for (int F=0;F<100;F++)
    {
        int j=1;
        while (j<=Q[F])
        {
            int x=qx[F][j],y=qy[F][j++];
            ans=max(ans,sqr(x-sx)+sqr(y-sy));
            for (int i=0;i<4;i++)
            {
                int xx=x+dx[i],yy=y+dy[i];
                if (xx>=0 && yy>=0 && xx<m && yy<n && d[xx][yy]!=step)
                {
                    f[xx][yy]=f[x][y]+a[xx][yy];
                    if (f[xx][yy]>k) continue;
                    push(f[xx][yy],xx,yy);
                }
            }
        }
    }
}

int main()
{
    string s;
    cin >> m >> n >> k;
    for (int i=0;i<m;i++) 
    {
        cin >> s;
        for (int j=0;j<n;j++) a[i][j]=s[j]-'0';
    }
    for (int i=0;i<m;i++)
        for (int j=0;j<n;j++)
            if (sqr(max(i,n-i))+sqr(max(j,n-j))>ans)
                visit(i,j);
    cout << ans << endl;
}

Code mẫu của RR

#include <iostream>
#include <algorithm>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <string>
#include <vector>
#include <queue>
#include <stack>
#include <map>
#include <set>
#include <iomanip>
#include <bitset>
#include <complex>

#define FOR(i,a,b) for(int i = a; i <= b; ++i)
#define FORD(i,a,b) for(int i = a; i >= b; --i)
#define REP(i,a) for(int i = 0; i < a; ++i)
#define MP make_pair
#define PB push_back
#define F first
#define S second
using namespace std;

int n, m, k, d[55][55];
char a[55][55];

deque< pair<int,int> > q;

const int di[] = {-1,1,0,0};
const int dj[] = {0,0,-1,1};

inline bool outside(const pair<int,int> &a) {
    if (a.F < 1 || a.F > m || a.S < 1 || a.S > n) return true;
    return false;
}

void bfs(int startu, int startv) {
    while (!q.empty()) q.pop_back();
    q.push_front(MP(startu, startv));
    memset(d, -1, sizeof d);
    if (a[startu][startv] == '0') d[startu][startv] = 0;
    else {
        if (k == 0) return ;
        d[startu][startv] = 1;
    }
    pair<int,int> u, v;
    while (!q.empty()) {
        u = q.front(); q.pop_front();
        REP(dir,4) {
            v = MP(u.F + di[dir], u.S + dj[dir]);
            if (outside(v) || d[v.F][v.S] >= 0) continue;

            if (a[v.F][v.S] == '0') {
                q.push_front(v);
                d[v.F][v.S] = d[u.F][u.S];
            }
            else if (d[u.F][u.S] < k) {
                q.push_back(v);
                d[v.F][v.S] = d[u.F][u.S] + 1;
            }
        }
    }
}

#define sqr(x) ((x) * (x))

int main() {
    scanf("%d%d%d\n", &m, &n, &k);
    FOR(i,1,m) scanf("%s\n", &a[i][1]);
    int res = 0;
    FOR(i,1,m) FOR(j,1,n) {
        bfs(i,j);
        FOR(ii,1,m) FOR(jj,1,n) if (d[ii][jj] >= 0) {
            res = max(res, sqr(i-ii) + sqr(j-jj));
        }
    }
    cout << res << endl;
    return 0;
}

Code mẫu của hieult

#include <set>
#include <map>
#include <list>
#include <cmath>
#include <queue>
#include <stack>
#include <cstdio>
#include <string>
#include <vector>
#include <cstdlib>
#include <cstring>
#include <sstream>
#include <iomanip>
#include <iostream>
#include <algorithm>

#include <ctime>
#include <deque>
#include <bitset>
#include <cctype>
#include <utility>
#include <cassert>

using namespace std;

typedef long long ll;
typedef long double ld;
typedef unsigned int ui;
typedef unsigned long long ull;

#define Rep(i,n) for(int i = 0; i < (n); ++i)
#define Repd(i,n) for(int i = (n)-1; i >= 0; --i)
#define For(i,a,b) for(int i = (a); i <= (b); ++i)
#define Ford(i,a,b) for(int i = (a); i >= (b); --i)
#define Fit(i,v) for(__typeof((v).begin()) i = (v).begin(); i != (v).end(); ++i)
//#define Fitd(i,v) for(__typeof((v).rbegin()) i = (v).rbegin(); i != (v).rend(); ++i)
#define mp make_pair
#define pb push_back
#define fi first
#define se second
#define sz(a) ((int)(a).size())
#define all(a) (a).begin(), (a).end()
#define ms(a,x) memset(a, x, sizeof(a))

template<class F, class T> T convert(F a, int p = -1) { stringstream ss; if (p >= 0) ss << fixed << setprecision(p); ss << a; T r; ss >> r; return r; }
template<class T> T gcd(T a, T b) { T r; while (b != 0) { r = a % b; a = b; b = r; } return a; }
template<class T> T lcm(T a, T b) { return a / gcd(a, b) * b; }
template<class T> T sqr(T x) { return x * x; }
template<class T> T cube(T x) { return x * x * x; }
template<class T> int getbit(T s, int i) { return (s >> i) & 1; }
template<class T> T onbit(T s, int i) { return s | (T(1) << i); }
template<class T> T offbit(T s, int i) { return s & (~(T(1) << i)); }
template<class T> int cntbit(T s) { return s == 0 ? 0 : cntbit(s >> 1) + (s & 1); }

const int bfsz = 1 << 16;
char bf[bfsz + 5];
int rsz = 0;
int ptr = 0;
char gc() {
    if (rsz <= 0) {
        ptr = 0;
        rsz = (int) fread(bf, 1, bfsz, stdin);
        if (rsz <= 0)
            return EOF;
    }
    --rsz;
    return bf[ptr++];
}
void ga(char &c) {
    c = EOF;
    while (!isalpha(c))
        c = gc();
}
int gs(char s[]) {
    int l = 0;
    char c = gc();
    while (isspace(c))
        c = gc();
    while (c != EOF && !isspace(c)) {
        s[l++] = c;
        c = gc();
    }
    s[l] = '\0';
    return l;
}
template<class T> bool gi(T &v) {
    v = 0;
    char c = gc();
    while (c != EOF && c != '-' && !isdigit(c))
        c = gc();
    if (c == EOF)
        return false;
    bool neg = c == '-';
    if (neg)
        c = gc();
    while (isdigit(c)) {
        v = v * 10 + c - '0';
        c = gc();
    }
    if (neg)
        v = -v;
    return true;
}

typedef pair<int, int> II;

const ld PI = acos(-1.0);
const ld eps = 1e-9;

const int dr[] = {+1, -1, 0, 0};
const int dc[] = {0, 0, +1, -1};

const int inf = (int)1e9 + 5;
const ll linf = (ll)1e16 + 5;
const ll mod = (ll)1e9 + 7;

#define maxn 55

int n, m, k, a[maxn][maxn], f[maxn][maxn];
char s[maxn];
II que[maxn * maxn], que1[maxn * maxn];
int size, size1;

void gen(){
    freopen("in.txt", "w", stdout);
    cout << 50 << " " << 50 << " " << 10 << endl;
    Rep(i, 50){
        Rep(j, 50) cout << rand() % 2;
        puts("");
    }
}

bool inside(int r, int c){
    return r >= 0 && r < n && c >= 0 && c < m;
}

void solve(){
//  freopen("in.txt", "r", stdin);
    scanf("%d %d %d", &n, &m, &k);
    Rep(i, n){
        scanf("%s", s);
        Rep(j, m) a[i][j] = s[j] - '0';
    }

    int MAX = 0;
    int r, c, rr, cc;
    Rep(i, n) Rep(j, m){
        if(sqr(i) + sqr(j) <= MAX && sqr(n - 1 - i) + sqr(j) <= MAX && sqr(i) + sqr(m - 1 - j) <= MAX && sqr(n - 1 - i) + sqr(m - 1 - j) <= MAX) continue;
        ms(f, -1);
        f[i][j] = a[i][j];
        if(f[i][j] > k) continue;
        size = 0; que[size++] = mp(i, j);
        while(size){
            Rep(t, size){
                r = que[t].fi; c = que[t].se;
                MAX = max(MAX, sqr(r - i) + sqr(c - j));
                Rep(h, 4){
                    rr = r + dr[h];
                    cc = c + dc[h];
                    if(inside(rr, cc) && a[rr][cc] == 0 && f[rr][cc] == -1){
                        f[rr][cc] = f[r][c];
                        que[size++] = mp(rr, cc);
                    }
                }
            }
            size1 = 0;
            Rep(t, size){
                r = que[t].fi; c = que[t].se;
                Rep(h, 4){
                    rr = r + dr[h];
                    cc = c + dc[h];
                    if(inside(rr, cc) && a[rr][cc] == 1 && f[rr][cc] == -1 && f[r][c] < k){
                        f[rr][cc] = f[r][c] + 1;
                        que1[size1++] = mp(rr, cc);
                    }
                }
            }

            size = 0;
            Rep(t, size1){
                que[size++] = que1[t];
            }
        }
    }

    cout << MAX << endl;
//  cout << clock() << endl;
}

int  main()
{
//  gen();
    solve();

    return 0;
}

Code mẫu của ll931110

#include <algorithm>
#include <bitset>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
#include <deque>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <utility>
#include <vector>
#define maxn 55
using namespace std;

int dx[4] = {-1,0,1,0};
int dy[4] = {0,1,0,-1};
int m,n,k;
string board[maxn];
int d[maxn][maxn];

int BFS(int sx,int sy) {
    memset(d,-1,sizeof(d));
    d[sx][sy] = (board[sx][sy] == '1') ? 1 : 0;
    deque< pair<int,int> > q;
    if (k >= d[sx][sy]) q.push_back(make_pair(sx,sy));
    while (!q.empty()) {
        int ux = q.front().first,uy = q.front().second;
        q.pop_front();
        for (int i = 0; i < 4; i++) {
            int vx = ux + dx[i],vy = uy + dy[i];
            if (vx < 0 || vx >= m || vy < 0 || vy >= n) continue;
            int tmp = d[ux][uy];
            if (board[vx][vy] == '1') tmp++;
            if (d[vx][vy] < 0 || d[vx][vy] > tmp) d[vx][vy] = tmp; else continue;
            if (d[vx][vy] == d[ux][uy]) q.push_front(make_pair(vx,vy)); else if (d[vx][vy] <= k) q.push_back(make_pair(vx,vy));
        }
    }
    int ans = 0;
    for (int i = 0; i < m; i++)
      for (int j = 0; j < n; j++)
        if (d[i][j] >= 0 && d[i][j] <= k) ans = max(ans,(sx - i) * (sx - i) + (sy - j) * (sy - j));
    return ans;
}

int main() {
//    freopen("1.in","r",stdin);
    scanf("%d %d %d", &m, &n, &k);
    for (int i = 0; i < m; i++) cin >> board[i];
    int ret = 0;
    for (int i = 0; i < m; i++)
      for (int j = 0; j < n; j++) ret = max(ret,BFS(i,j));
    printf("%d\n", ret);
}