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N Knights Problem CodeChef Solution
Problem -N Knights Problem CodeChef Solution
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N Knights Problem CodeChef Solution in C++14
#include<bits/stdc++.h>
#define int long long
#define MAXN 50010
#define MAXM 500010
using namespace std;
const int inf=0x3f3f3f3f3f3f3f3f;
const int dx[8]={1,2,2,1,-1,-2,-2,-1};
const int dy[8]={2,1,-1,-2,-2,-1,1,2};
int T,n,m;
char mp[1010][1010];
struct Node{int to,nxt,flow;}Edge[MAXM];
int Head[MAXN],cnt_Edge=1;
void add(int u,int v,int w){
Edge[++cnt_Edge]=(Node){v,Head[u],w};
Head[u]=cnt_Edge;
}
void Add_Edge(int u,int v,int w){add(u,v,w);add(v,u,0);}
int cur[MAXN],dep[MAXN],q[MAXN],l,r;
bool bfs(int s,int t){
q[l=r=1]=s;memset(dep,0,sizeof(dep));
dep[s]=1;memcpy(cur,Head,sizeof(cur));
while(l<=r){
int u=q[l++];
for(int i=Head[u];i;i=Edge[i].nxt){
int v=Edge[i].to,w=Edge[i].flow;
if(!w||dep[v])continue;
dep[v]=dep[u]+1;q[++r]=v;
if(v==t)return true;
}
}return false;
}
int dfs(int u,int t,int flow){
int rest=flow;if(u==t)return flow;
for(int i=cur[u];i&&rest;i=Edge[i].nxt){
cur[u]=i;int v=Edge[i].to,w=Edge[i].flow;
if(!w||dep[v]!=dep[u]+1)continue;
int now=dfs(v,t,min(rest,w));
if(!now)dep[v]=-1;
rest-=now;Edge[i].flow-=now;
Edge[i^1].flow+=now;
}return flow-rest;
}
int dinic(int s,int t){
int ret=0;
while(bfs(s,t)){
int flow=0;
while((flow=dfs(s,t,inf)))
ret+=flow;
}return ret;
}
int get(int x,int y){return (x-1)*m+y;}
signed main(){
scanf("%lld",&T);
while(T--){
memset(Head,0,sizeof(Head));cnt_Edge=1;
scanf("%lld%lld",&n,&m);int cnt=0;
for(int i=1;i<=n;i++)scanf("%s",mp[i]+1);
for(int i=1;i<=n;i++)
for(int j=1;j<=m;j++){
int u=get(i,j);if(mp[i][j]=='#')continue;cnt++;
if(!((i+j)&1))continue;
for(int d=0;d<8;d++){
int x=i+dx[d],y=j+dy[d];
if(x>0&&x<=n&&y>0&&y<=m&&mp[x][y]=='.')Add_Edge(u,get(x,y),1);
}
}
int s=n*m+1,t=s+1;
for(int i=1;i<=n;i++)
for(int j=1;j<=m;j++){
if(mp[i][j]=='#')continue;
if((i+j)&1)Add_Edge(s,get(i,j),1);
else Add_Edge(get(i,j),t,1);
}
printf("%lld\n",cnt-dinic(s,t));
}
return 0;
}N Knights Problem CodeChef Solution in PYTH 3
# cook your dish here
import random
dy = [-2, -1, 1, 2, -2, -1, 1, 2]
dx = [-1, -2, -2, -1, 1, 2, 2, 1]
class Ponies:
mat = []
G = []
match = []
used = []
def dfs(self, v):
global used
used.add(v)
for i in range(len(G[v])):
u = G[v][i]
w = match[u]
if w < 0 or w not in used and self.dfs(w):
match[v] = u
match[u] = v
return 1
return 0
def bipartiteMatching(self, V):
global used
global match
res = 0
match = [-1] * 1500
for v in range(V):
if match[v] < 0:
used = set([])
if self.dfs(v):
res += 1
return res
def maxIndependentSet(self, h, w, V):
global G
G = [[] for _ in range(1500)]
for i in range(h):
for j in range(w):
if mat[i][j] == -1:
continue
curr = mat[i][j]
for k in range(8):
y = i + dy[k]
x = j + dx[k]
if y < 0 or y >= h or x < 0 or x >= w or mat[y][x] == -1:
continue
G[curr] += [mat[y][x]]
maximalIndependentSet = V - self.bipartiteMatching(V)
return maximalIndependentSet
def solve(self, chessboard):
global mat
V = 0
mat = [[0 for _ in range(50)] for _ in range(50)]
h = len(chessboard)
w = len(chessboard[0])
for i in range(h):
for j in range(w):
if chessboard[i][j] == '.':
V += 1
mat[i][j] = V
else:
mat[i][j] = -1 # wall
return self.maxIndependentSet(h, w, V)
# TEST_CASES = 90
# MIN_WIDTH =25
# MAX_WIDTH = 30
# MIN_HEIGHT = 25
# MAX_HEIGHT = 30
solver = Ponies()
# def generate_test_case():
# h = random.randint(MIN_HEIGHT, MAX_HEIGHT)
# w = random.randint(MIN_WIDTH, MAX_WIDTH)
# allowed_chars = ['#', '.']
# input_mat = []
# for _ in range(h):
# row = ''
# for _ in range(w):
# char_idx = random.randint(0, 1)
# row += allowed_chars[char_idx]
# input_mat += [row]
# solution = solver.solve(input_mat)
# test_case = '{\"' + '\",\"'.join(input_mat) + '\"},' + str(solution)
# print(test_case)
# for _ in range(TEST_CASES):
# generate_test_case()
T = int(input())
while T:
T -= 1
h, w = [int(entry) for entry in input().split(' ')]
input_mat = []
for _ in range(h):
row = input()
input_mat += [row]
print(solver.solve(input_mat))
N Knights Problem CodeChef Solution in C
#include <stdio.h>
#include <string.h>
#define S(a) memset(a,0,sizeof(a));
#define T(a,b) for(a=0;a<b;a++)
#define U(a,b,c) for(a=1;a<=(n*m-1)/2+1;a++)if(b)c
int id, xi[8]={-2,-1,1,2,2,1,-1,-2},yi[8]={1,2,2,1,-1,-2,-2,-1}, X[6][9100];
int A(int x)
{
int i=X[0][x];
if(X[3][x]==id) return 0;
for(X[3][x]=id; i; i=X[4][i])
if(!X[1][X[5][i]]||A(X[1][X[5][i]]))
return 1+(X[2][X[1][X[5][i]]=x]=X[5][i])*0;
return 0;
}
main()
{
int fall, i, j, l, x, y, n, m, e, v, d[33][33];
char a[33][33];
for(scanf("%d",&fall); fall--; printf("%d\n", v))
{
for(i=!scanf("%d %d\n",&n,&m); i<n; gets(a[i++]));
S(X[0])S(X[1])S(X[2])S(X[3])
for(i=e=v=0;i<n;i++)T(j,m)d[i][j]=(i*m+j)/2+1+(v+=a[i][j]!='#')*0;
T(i,n)T(j,m)if(a[i][j]!='#'&&((i+j)&1))T(l,8)if(!(a[x=i+xi[l]][y=j+yi[l]]=='#'||x<0||y<0||n<=x||m<=y))
X[1][d[x][y]]=((!!(X[5][++e]=d[x][y])||!X[5][e])&&(!!(X[4][e]=X[0][d[i][j]])||!X[4][e])&&(!!(X[0][d[i][j]]=e)||!e)&&!X[2][d[i][j]]&&!X[1][d[x][y]])?(d[i][j]+(X[2][d[i][j]]=d[x][y])*0):X[1][d[x][y]];
U(id,!X[2][id],A(id));
U(i,X[2][i],v--);
}
return 0;
}
N Knights Problem CodeChef Solution in JAVA
import java.util.*;
import java.io.*;
import static java.lang.Math.*;
public class Main{
public static void main(String[] args){
try{
new Main().run();
}catch (Exception e){
}
}
void run() throws Exception{
BufferedReader sc = new BufferedReader(new InputStreamReader(System.in));//new Scanner(System.in);
int T = Integer.parseInt(sc.readLine());
final int[] dx = new int[]{2,1,-1,-2,-2,-1,1,2};
final int[] dy = new int[]{1,2,2,1,-1,-2,-2,-1};
for(;T>0;T--){
String[] hw = sc.readLine().split(" ");
int h = Integer.parseInt(hw[0]);
int w = Integer.parseInt(hw[1]);
int total = h*w;
char[][] f = new char[h][w];
for(int i = 0; i < h; i++)f[i] = sc.readLine().toCharArray();
int[][] id = new int[h][w];
int count = 1;
for(int i = 0; i < h; i++)for(int j = 0; j < w; j++)if(f[i][j] == '.')id[i][j] = count++;
count++;
V[] nodes = new V[count];
int[][] graph = new int[count][count];
for(int i = 0; i < count; i++)nodes[i] = new V();
for(int i = 0; i < h; i++)
for(int j = 0; j < w; j++){
if(f[i][j] == '.'){
int ind = id[i][j];
boolean left = (i+j) % 2 == 0;
for(int k = 0; k < dx.length; k++){
int ny = i + dy[k];
int nx = j + dx[k];
if(ny < 0 || ny >= h || nx < 0 || nx >= w || f[ny][nx] == '#')
continue;
int jnd = id[ny][nx];
//nodes[ind].add(nodes[jnd], 1);
if(left)graph[ind][jnd] = 1;
else graph[jnd][ind] = 1;
}
if(left)
graph[0][ind] = 1;
else
graph[ind][count-1] = 1;
}
}
for(int i = 0; i < count; i++)
for(int j = 0; j < count; j++)
if(graph[i][j] == 1){
nodes[i].add(nodes[j], 1);
}
int match = SDinic.dinic(nodes[0], nodes[count-1]);
System.out.println(count-2-match);
}
}
}
class SDinic{
static final int INF = Integer.MAX_VALUE;
static int dinic(V s, V t){
int flow = 0;
for(int p = 1; ; p++){
Queue<V> que = new LinkedList<V>();
s.level = 0;
s.p = p;
que.offer(s);
while(!que.isEmpty()){
V v = que.poll();
v.iter = v.es.size()-1;
for(E e : v.es)
if(e.to.p < p && e.cap > 0){
e.to.level = v.level + 1;
e.to.p = p;
que.offer(e.to);
}
}
if(t.p < p)
return flow;
for(int f; (f = dfs(s, t, INF)) > 0;)
flow += f;
}
}
static int dfs(V v, V t, int f){
if(v == t)
return f;
for(; v.iter >= 0; v.iter--){
E e = v.es.get(v.iter);
if(v.level < e.to.level && e.cap > 0){
int d = dfs(e.to, t, Math.min(f, e.cap));
if(d > 0){
e.cap -= d;
e.rev.cap += d;
return d;
}
}
}
return 0;
}
}
class V{
ArrayList<E> es = new ArrayList<E>();
int level, p, iter;
void add(V to, int cap){
E e = new E(to, cap), rev = new E(this, 0);
e.rev = rev; rev.rev = e;
es.add(e); to.es.add(rev);
}
}
class E{
V to;
E rev;
int cap;
E(V to, int cap){
this.to = to;
this.cap = cap;
}
}N Knights Problem CodeChef Solution in GO
package main
import (
"bufio"
"bytes"
"fmt"
"os"
)
func readInt(bytes []byte, from int, val *int) int {
i := from
sign := 1
if bytes[i] == '-' {
sign = -1
i++
}
tmp := 0
for i < len(bytes) && bytes[i] >= '0' && bytes[i] <= '9' {
tmp = tmp*10 + int(bytes[i]-'0')
i++
}
*val = tmp * sign
return i
}
func readNum(reader *bufio.Reader) (a int) {
bs, _ := reader.ReadBytes('\n')
readInt(bs, 0, &a)
return
}
func readTwoNums(reader *bufio.Reader) (a int, b int) {
res := readNNums(reader, 2)
a, b = res[0], res[1]
return
}
func readThreeNums(reader *bufio.Reader) (a int, b int, c int) {
res := readNNums(reader, 3)
a, b, c = res[0], res[1], res[2]
return
}
func readNNums(reader *bufio.Reader, n int) []int {
res := make([]int, n)
x := 0
bs, _ := reader.ReadBytes('\n')
for i := 0; i < n; i++ {
for x < len(bs) && (bs[x] < '0' || bs[x] > '9') && bs[x] != '-' {
x++
}
x = readInt(bs, x, &res[i])
}
return res
}
func readUint64(bytes []byte, from int, val *uint64) int {
i := from
var tmp uint64
for i < len(bytes) && bytes[i] >= '0' && bytes[i] <= '9' {
tmp = tmp*10 + uint64(bytes[i]-'0')
i++
}
*val = tmp
return i
}
func main() {
reader := bufio.NewReader(os.Stdin)
var buf bytes.Buffer
tc := readNum(reader)
for tc > 0 {
tc--
m, n := readTwoNums(reader)
G := make([][]byte, m)
for i := 0; i < m; i++ {
G[i], _ = reader.ReadBytes('\n')
}
res := solve(m, n, G)
buf.WriteString(fmt.Sprintf("%d\n", res))
}
fmt.Print(buf.String())
}
func solve(m, n int, G [][]byte) int {
N := m * n
g := NewGraph(N, N*N)
connect := func(u, v int) {
a, b := u/n, u%n
if (a^b)&1 == 1 {
g.AddEdge(u, v)
} else {
g.AddEdge(v, u)
}
}
for i := 0; i < m; i++ {
for j := 0; j < n; j++ {
if G[i][j] == '#' {
continue
}
if i+1 < m && j+2 < n && G[i+1][j+2] == '.' {
u := i*n + j
v := (i+1)*n + j + 2
connect(u, v)
}
if i+1 < m && j-2 >= 0 && G[i+1][j-2] == '.' {
u := i*n + j
v := (i+1)*n + j - 2
connect(u, v)
}
if i+2 < m && j+1 < n && G[i+2][j+1] == '.' {
u := i*n + j
v := (i+2)*n + j + 1
connect(u, v)
}
if i+2 < m && j-1 >= 0 && G[i+2][j-1] == '.' {
u := i*n + j
v := (i+2)*n + j - 1
connect(u, v)
}
}
}
pair := make([]int, N)
for i := 0; i < N; i++ {
pair[i] = -1
}
seen := make([]int, N)
var dfs func(u int, cur int) bool
dfs = func(u int, cur int) bool {
if seen[u] == cur {
return false
}
seen[u] = cur
for i := g.nodes[u]; i > 0; i = g.next[i] {
v := g.to[i]
if pair[v] < 0 || dfs(pair[v], cur) {
pair[v] = u
return true
}
}
return false
}
var res int
for i := 0; i < m; i++ {
for j := 0; j < n; j++ {
if G[i][j] == '.' {
res++
if (i^j)&1 == 1 && pair[i*n+j] < 0 && dfs(i*n+j, i*n+j+1) {
res--
}
}
}
}
return res
}
type Graph struct {
nodes []int
next []int
to []int
cur int
}
func NewGraph(n int, e int) *Graph {
nodes := make([]int, n)
next := make([]int, e+10)
to := make([]int, e+10)
return &Graph{nodes, next, to, 0}
}
func (g *Graph) AddEdge(u, v int) {
g.cur++
g.next[g.cur] = g.nodes[u]
g.nodes[u] = g.cur
g.to[g.cur] = v
}N Knights Problem CodeChef Solution Review:
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