法1:二维DP
必须掌握!
java
class Solution {
public int uniquePaths(int m, int n) {
int[][] matrix = new int[m][n];
Arrays.fill(matrix[0], 1);
for (int i = 0; i < m; ++i) {
matrix[i][0] = 1;
}
for (int i = 1; i < m; ++i) {
for (int j = 1; j < n; ++j) {
matrix[i][j] = matrix[i - 1][j] + matrix[i][j - 1];
}
}
return matrix[m - 1][n - 1];
}
}