1923. Scary Politics (timus) (dfs) search

Posted 2020-10-29 wz30

http://acm.timus.ru/problem.aspx?space=1&num=1923 -- timus

This is s problem about thd dfs and searching like the leetcode islands problems

Creating three 2-D arrays: board, land(copy), visit.

board: the input, land:(0: undecided, 1: B country, 2: M country), visit

invading the land one by one. 

for each fill, operation:

if land[i][j] = enemy return;

if land[i][j] = 0 && board[i][j] = alliance: land[i][j] = empire // 1 or 2

if land[i][j] = empire; check the neighbors of each location from board.

 

Heads-up: checking the boundary and visited(stack overflow)

import java.util.Scanner;

public class timus1923 {
    static int visit[][] = new int[55][55];
    //empire B: 1, M:2, a: original land, copy: terriority
    static void fill(int x, int y, int alligance, int empire,int a[][], int copy[][],int n, int m){
        if(x<0 || y<0 || x>=n || y>=m) return;//our of boundary
        //check the empire board
        if(visit[x][y] == 1) return;
        visit[x][y] = 1;
        int enemy = 0;
        if(empire==1) enemy = 2;
        else enemy =1;

        if(copy[x][y] == enemy) return;//enemy‘s land
        if(copy[x][y]==0 && a[x][y] == alligance) copy[x][y] = empire;
        if(copy[x][y]==empire) {
            fill(x-1,y,alligance,empire,a,copy,n,m);
            fill(x,y-1,alligance,empire,a,copy,n,m);
            fill(x+1,y,alligance,empire,a,copy,n,m);
            fill(x,y+1,alligance,empire,a,copy,n,m);
        }

    }
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int m = in.nextInt();
        int a[][] = new int[n+1][m+1];
        int copy[][] = new int[n+1][m+1];// emprire land
        //int tag[] = new int[5];

        for(int i = 0; i<n; i++){
            String str = in.next();
            for(int j = 0; j< m; j++){
                a[i][j] = str.charAt(j)-‘0‘;
                //tag[a[i][j]] ++;
            }
        }
        int l = in.nextInt();
        int b[] = new int[l+1];
        for(int i = 0; i<l; i++){
            b[i] = in.nextInt();
        }
        int countB = 0;
        int countM = 0;
        copy[n-1][0] = 1;
        copy[0][m-1] = 2;
        //start from
        fill(n-1,0,a[n-1][0],1,a,copy,n,m);
        fill(0,m-1,a[0][m-1],2,a,copy,n,m);

        for(int i = 0; i<l; i++){
            //init visi
            for(int j = 0; j<55; j++){
                for(int k = 0; k<55; k++){
                    visit[j][k] = 0;
                }
            }

            if(i%2==0){
                fill(n-1,0,b[i],1,a,copy,n,m);
            }else{
                fill(0,m-1,b[i],2,a,copy,n,m);
            }
        }
        for(int i  =0; i<n; i++){
            for(int j = 0; j<m; j++){
                if(copy[i][j] == 1) countB++;
                else if(copy[i][j] == 2) countM++;
            }
        }

        System.out.println(countB);
        System.out.println(countM);
    }
}

 

Life is funny.