Codeforces 515D Drazil and Tiles <路径dfs +="" 跳格=""> __ Solution strategy: Recursion

Topic: Http://codeforces.com/problemset/problem/515/D : Give you a square, ask you to fill the square with 1x2, some squares have been occupied (with ' * '), not occupied ('. ') ）。 Put up to fill, with "^v" said, horizontal up, with "<>" said. If you put the method unique, the output of the square chart. Otherwise, the output is not unique. Analysis: DFS, a pair of to find. Input

3 3
...
.*.
...

Output

Not unique

Input

4 4
.. **
*...
*.**
....

Output

<>**
*^<>
*v**
<><>

#include <bits/stdc++.h> using namespace std;
int const MAX = 2010;
Char S[max][max];
int n, m, CNT;
int dx[4] = {0, 0, 1,-1};

int dy[4] = {1,-1, 0, 0};
        void Dfs (int x, int y) {if (x < 1 | | x > N | | y < 1 | | y > M | | s[x][y]!= '. ')
    Return
    int dir =-1, sum = 0;
        for (int i = 0; i < 4; i++) {int xx = x + dx[i];
        int yy = y + dy[i];
        if (s[xx][yy] = = '. ')
            {sum + +;
        dir = i;
            } if (sum = = 1) {if (dir = = 0) {S[x][y] = ' < ';
        S[x][y + 1] = ' > ';
            else if (dir = = 1) {S[x][y] = ' > ';
        S[x][y-1] = ' < ';
            else if (dir = = 2) {S[x][y] = ' ^ ';
        S[x + 1][y] = ' V ';
            else if (dir = = 3) {S[x][y] = ' V ';
        S[x-1][y] = ' ^ ';
        CNT = 2;
   for (int i = 0; i < 4; i++)         DFS (x + dx[dir] + dx[i], y + dy[dir] + dy[i]);
    } void Init () {cnt = 0; for (int i = 1; I <= n; i++) for (int j = 1; j <= m; j) if (s[i][j] = = ' * ') CNT +
+;
    int main () {scanf ("%d%d", &n, &m);
    for (int i = 1; I <= n; i++) scanf ("%s", S[i] + 1);
    Init ();
    for (int i = 1; I <= n; i++) for (int j = 1; j <= m; j) Dfs (I, j);
        if (CNT = n * m) {for (int i = 1; I <= n; i++) {printf ("%s\n", S[i] + 1);
    else printf ("Not unique\n");
return 0;
 }