数组写法

#include <cstring>
#include <iostream>
#include <algorithm>
#include <vector>

#define x first
#define y second

using namespace std;

typedef pair<int, int> PII;

const int N = 5;

char g[N][N], backup[N][N];

int get(int x, int y)
{
    return x * 4 + y;
}

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

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);
}

int main()
{
    for (int i = 0; i < 4; i ++ ) cin >> g[i];

    vector<PII> res;
    for (int op = 0; op < 1 << 16; op ++ )
    {
        vector<PII> temp;
        memcpy(backup, g, sizeof g);        // 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)
                {
                    temp.push_back({i, j});
                    turn_all(i, j);
                }

        // 判断所有灯泡是否全亮
        bool has_closed = false;
        for (int i = 0; i < 4; i ++ )
            for (int j = 0; j < 4; j ++ )
                if (g[i][j] == '+')
                    has_closed = true;

        if (has_closed == false)
        {
            if (res.empty() || res.size() > temp.size()) res = temp;
        }

        memcpy(g, backup, sizeof g);        // 还原
    }

    cout << res.size() << endl;
    for (auto op : res) cout << op.x + 1 << ' ' << op.y + 1 << endl;

    return 0;
}

位运算写法

#include <cstring>
#include <iostream>
#include <algorithm>
#include <vector>

using namespace std;

typedef pair<int,int> PII;
const int N = 4, INF = 100;

int change[N][N];

int get(int x, int y)
{
    return x * N + y;
}

int main()
{
    for (int i = 0; i < N; i ++ )
        for (int j = 0; j < N; j ++ )
        {
            for (int k = 0; k < N; k ++ ) change[i][j] += (1 << get(i, k)) + (1 << get(k, j));
            change[i][j] -= 1 << get(i, j);
        }

    int state = 0;
    for (int i = 0; i < N; i ++ )
    {
        string line;
        cin >> line;
        for (int j = 0; j < N; j ++ )
            if (line[j] == '+')
                state += 1 << get(i, j);
    }

    vector<PII> path;
    for (int i = 0; i < 1 << 16; i ++ )
    {
        int now = state;
        vector<PII> temp;
        for (int j = 0; j < 16; j ++ )
            if (i >> j & 1)
            {
                int x = j / 4, y = j % 4;
                now ^= change[x][y];
                temp.push_back({x, y});
            }
        if (!now && (path.empty() || path.size() > temp.size())) path = temp;
    }

    cout << path.size() << endl;
    for (auto &p : path)
        cout << p.first + 1 << ' ' << p.second + 1 << endl;

    return 0;
}