class Solution {

public int uniquePaths(int m, int n) {

int[][] pathN = new int[m][n];

boolean[][] visited = new boolean[m][n];

pathN[0][0] = 1;

bfs(pathN, visited);

return pathN[m-1][n-1];

}

public void bfs(int[][] pathN, boolean[][] visited){

Queue<Pair> paths = new LinkedList<>();

int[] mx = {0, 1};

int[] my = {1, 0};

paths.offer(new Pair(0,0));

while(!paths.isEmpty()){

Pair p = paths.poll();

for(int i = 0; i < 2; i++){

int nx = mx[i] + p.x;

int ny = my[i] + p.y;

if(nx >= pathN.length || ny >= pathN[0].length) continue;

pathN[nx][ny] += pathN[p.x][p.y];

if(!visited[nx][ny]){

paths.offer(new Pair(nx, ny));

visited[nx][ny] = true;

}

}

}

}

class Pair{

int x;

int y;

Pair(int x, int y){

this.x = x;

this.y = y;

}

}

}