dfs

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.util.ArrayList;
import java.util.List;

public class Main {
    private static final int N = 4;
    private static char[][] g = new char[N][N];
    private static List<Node> ans = new ArrayList<>();
    private static List<Node> tmp = new ArrayList<>();
    private static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    private static BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));

    static class Node {
        int x;
        int y;
        public Node(int x, int y) {
            this.x = x;
            this.y = y;
        }
    }

    private static void turn_one(int x, int y) {
        if (g[x][y] == '+') g[x][y] = '-';
        else g[x][y] = '+';
    }

    private static void turn_all(int x, int y) {
        for (int i = 0; i < 4; i ++) {
            turn_one(x, i);
            turn_one(i, y);
        }
        turn_one(x, y);
    }

    private static boolean check() {
        for (int i = 0; i < 4; i ++)
            for (int j = 0; j < 4; j ++)
                if (g[i][j] == '+')
                    return false;

        return true;
    }

    private static void dfs(int x, int y) {
        // 所有的把手都操作完了。
        if (x == 3 && y == 4) {
            if (check()) {
                if (ans.isEmpty() || ans.size() > tmp.size())
                    ans = new ArrayList<>(tmp);
            }
            return;
        }

        // 判断边界，如果y出界则移动到下一行
        if (y == 4) {
            x ++;
            y = 0;
        }

        // 操作把手(x, y)
        turn_all(x, y);
        tmp.add(new Node(x, y));

        dfs(x, y + 1);
        // 恢复现场
        tmp.remove(tmp.size() - 1);
        turn_all(x, y);

        // 不操作把手
        dfs(x, y + 1);
    }

    public static void main(String[] args) throws IOException {
        for (int i = 0; i < 4; i ++) g[i] = br.readLine().toCharArray();

        dfs(0, 0);

        bw.append(ans.size() + "\n");
        for (Node op: ans) {
            bw.append((op.x + 1) + " " + (op.y + 1) + "\n");
        }

        br.close();
        bw.flush();
        bw.close();

    }
}

二进制

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.util.ArrayList;
import java.util.List;

public class Main {
    private static final int N = 4;
    private static char[][] g = new char[N][N];
    private static char[][] backup = new char[N][N];
    private static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    private static BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));

    static class Node {
        int x;
        int y;
        public Node(int x, int y) {
            this.x = x;
            this.y = y;
        }
    }

    // 二维坐标转换一维
    private static int get(int x, int y) {
        return x * 4 + y;
    }

    private static void turn_one(int x, int y) {
        if (g[x][y] == '+') g[x][y] = '-';
        else g[x][y] = '+';
    }

    private static void turn_all(int x, int y) {
        for (int i = 0; i < 4; i ++) {
            turn_one(x, i);
            turn_one(i, y);
        }
        turn_one(x, y);
    }

    private static boolean check() {
        for (int i = 0; i < 4; i ++)
            for (int j = 0; j < 4; j ++)
                if (g[i][j] == '+')
                    return false;

        return true;
    }


    public static void main(String[] args) throws IOException {
        for (int i = 0; i < 4; i ++) g[i] = br.readLine().toCharArray();

        List<Node> res = new ArrayList<>(); 
        for (int op = 0; op < 1 << 16; op ++) {
            List<Node> tmp = new ArrayList<>();
            for (int i = 0; i < 4; i ++) System.arraycopy(g[i], 0, backup[i], 0, N); // 备份

            // 进行操作
            for (int i = 0; i < 4; i ++)
                for (int j = 0; j < 4; j ++)
                    if ((op >> get(i, j) & 1) == 1) {
                        tmp.add(new Node(i, j));
                        turn_all(i, j);
                    }

            // 判断所有开关是否全打开
            if (check()) {
                if (res.isEmpty() || res.size() > tmp.size())
                    res = new ArrayList<>(tmp);
            }

            for (int i = 0; i < 4; i ++) System.arraycopy(backup[i], 0, g[i], 0, N); // 还原

        }

        bw.append(res.size() + "\n");
        for (Node op: res) bw.append((op.x + 1) + " " + (op.y + 1) + "\n");


        br.close();
        bw.flush();
        bw.close();

    }
}