map[i][j] = map[i-1][j] + map[i][j-1]
class Solution {
public int[][] map;
public int uniquePaths(int m, int n) {
map = new int[m][];
for (int i = 0; i < m; i++)
map[i] = new int[n];
//계산 시작
map[0][0] = 1;
for (int i = 0; i < m; i++) {
for (int j = 0; j < n; j++) {
if (i != 0) map[i][j] += map[i-1][j];
if (j != 0) map[i][j] += map[i][j-1];
}
}
return map[m-1][n-1];
}
}