poj3740

最新推荐文章于 2019-09-17 19:19:38 发布

原创最新推荐文章于 2019-09-17 19:19:38 发布 · 250 阅读

0 ·

CC 4.0 BY-SA版权

算法专栏收录该内容

35 篇文章

订阅专栏

本文介绍了一个关于矩阵覆盖的问题，并通过深度优先搜索算法进行求解。对于给定的M×N矩阵，每行包含若干个1，目标是通过选择部分行进行叠加，使得每一列恰好出现一次1，实现这一目标则输出成功信息。

package work;

import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;

public class A3740 {
static int[][] S;
static int M, N;
static boolean isfound;
static boolean[] row;
static int [] col;

public static void main(String[] args) throws FileNotFoundException {
  /* Scanner sc=new Scanner(System.in); */
  Scanner sc = new Scanner(new File("src/3740"));
  while (true) {
   M = sc.nextInt();
   N = sc.nextInt();
   S = new int[M][N];
   if (M == 0 && N == 0) {
    break;
   }
   for (int i = 0; i < M; i++) {
    for (int j = 0; j < N; j++) {
     S[i][j] = sc.nextInt();
    }
   }
   isfound = false;
   row = new boolean[M];
   col = new int[N];
   for (int m = 0; m < M; m++) {
    dfs(0,m);
    if(isfound){break;}
   }
   if (isfound) {
    System.out.println("Yes, I found it");
   } else {
    System.out.println("It is impossible");
   }
   //
   /*
    * for (int i = 0; i < M; i++) { for (int j = 0; j < N; j++) {
    * System.out.print(S[i][j]); } System.out.println(); }
    */
   //
  }
}

private static void dfs(int step,int m) {
  if (step==M) {
   return ;
  }
  row[step]=true;
  if(check(step,m)){
   if(isfound==true){return;}
   dfs(step+1,m);
  }
  else{
   row[step]=false;
   dfs(step+1,m);
  }
}

private static boolean check(int step,int m) {
  int num =0;
  boolean ret=false;
  for (int i = m; i <=step; i++) {
   if(row[i]){
    for (int j = 0; j < N; j++) {
     col[j]+=S[i][j];
     if(col[j]==1){num++;}
     else if(col[j]>1){ret =false;return ret;}
    }
    if(num==N){isfound=true;}
   }
  }
  return ret;
}

}

package work;

import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;

public class A3740 {
static int[][] S;
static int M, N;
static boolean isfound;
static boolean[] row;
static int [] col;