Fill_1221_coada

/// Solutie - Moca Andrei - 100p - Coada
#include <bits/stdc++.h>
using namespace std;
const int di[] {-1,  0, 1, 0};
const int dj[] { 0, -1, 0, 1};
const int N(1005);
char mat[N][N];
int n, m, iv, jv, cnt;
queue<pair<int, int>> q;
inline void Filleaza(int i, int j) {
    for (int dir = 0; dir < 4; ++dir) {
        iv = i + di[dir];
        jv = j + dj[dir];
        if (mat[iv][jv] == '.')
            q.emplace(iv, jv);
    }
}
int main() {
    scanf("%d%d", &n, &m);
    for (int i = 0; i <= n; ++i)
        gets(mat[i] + 1);
    for (int i = 1; i <= n; ++i)
        for (int j = 1; j <= m; ++j)
            if (mat[i][j] == '.')
                q.emplace(i, j);
    int i, j;
    while (!q.empty()) {
        tie(i, j) = q.front();
        q.pop();
        cnt = 0;
        if (mat[i][j] == '.') {
            for (int dir = 0; dir < 4; ++dir) {
                iv = i + di[dir];
                jv = j + dj[dir];
                cnt += (mat[iv][jv] == '.');
            }
            if (cnt == 1) {
                if (mat[i-1][j] == '.') {
                    mat[i-1][j] = '^', mat[i][j] = 'v';
                    Filleaza(i - 1, j);
                }
                if (mat[i][j-1] == '.') {
                    mat[i][j-1] = '<', mat[i][j] = '>';
                    Filleaza(i, j - 1);
                }
                if (mat[i+1][j] == '.') {
                    mat[i][j] = '^', mat[i+1][j] = 'v';
                    Filleaza(i + 1, j);
                }
                if (mat[i][j+1] == '.') {
                    mat[i][j] = '<', mat[i][j+1] = '>';
                    Filleaza(i, j + 1);
                }
            }
        }
    }
    for (int i = 1; i <= n; ++i)
        for (int j = 1; j <= m; ++j)
            if (mat[i][j] == '.') {
                printf("%s", "altadata");
                return 0;
            }
    for (int i = 1; i <= n; ++i)
        printf("%s\n", mat[i] + 1);
    return 0;
}