Run time error on empty input?

• Hi, I got a run time error on a empty input[ ]. my code works fine with my own test codes. Any idea of what is happening?

And I use empty char[ ][ ] to test on local machine, it works fine.

My algorithm is to start from 'o's on the edges of the board, then use a iterative DFS to find 'o' clique on the board. Then mark 'x' to other 'o's that are not connected to the edge 'o's.

``````public static void solve(char[][] board) {
if(board==null){
return;
}

if(board[0]==null){
return;
}

boolean[][] visited = new boolean[board.length][board.length];

for (int i = 0; i < board.length; i++) {
if (board[i][0] == 'o' && visited[i][0] == false) {
visited[i][0] = true;
findClique(i, 0, board, visited);
}
if (board[i][board[0].length - 1] == 'o'
&& visited[i][board[0].length - 1] == false) {
visited[i][board[0].length - 1] = true;
findClique(i, board[0].length - 1, board, visited);
}

}

for (int i = 0; i < board[0].length; i++) {
if (board[0][i] == 'o'&&visited[0][i] ==false) {
visited[0][i] = true;
findClique(0, i, board, visited);
}
if (board[board.length - 1][i] == 'o'&&visited[board.length - 1][i] == false) {
visited[board.length - 1][i] = true;
findClique(board.length - 1, i, board, visited);
}

}

for (int i = 0; i < board.length; i++) {
for (int m = 0; m < board[0].length; m++) {
if(board[i][m]=='o'&& visited[i][m]==false){
board[i][m] = 'x';
}
}
}

return;
}//

private static void findClique(int x, int y, char[][] board,
boolean[][] visited) {

visited[x][y] = false;

Stack<Integer> stx = new Stack<Integer>();
Stack<Integer> sty = new Stack<Integer>();
stx.push(x);
sty.push(y);

int xtmp = 0;
int ytmp = 0;
while (!stx.isEmpty()) {
xtmp = stx.pop();
ytmp = sty.pop();
visited[xtmp][ytmp] = true;

if (xtmp > 0) {
if (board[xtmp - 1][ytmp] == 'o'
&& visited[xtmp - 1][ytmp] == false) {
stx.push(xtmp - 1);
sty.push(ytmp);
}
}

if (xtmp < board.length - 1) {
if (board[xtmp + 1][ytmp] == 'o'
&& visited[xtmp + 1][ytmp] == false) {
stx.push(xtmp + 1);
sty.push(ytmp);
}
}

if (ytmp > 0) {
if (board[xtmp][ytmp - 1] == 'o'
&& visited[xtmp][ytmp - 1] == false) {
stx.push(xtmp);
sty.push(ytmp - 1);
}
}

if (ytmp < board[0].length - 1) {
if (board[xtmp][ytmp + 1] == 'o'
&& visited[xtmp][ytmp + 1] == false) {
stx.push(xtmp);
sty.push(ytmp + 1);
}
}

}

}``````

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