Leetcode unique paths

A robot is located at the top-left corner ofMXNGrid (marked 'start' in the dimo-below ).

The robot can only move either down or right at any point in time. The robot is trying to reach the bottom-right corner of the grid (marked 'finish 'in the dimo-below ).

How many possible unique paths are there?

Above is a 3x7 grid. How many possible unique paths are there?

Note: MAndNWill be at most 100.

 

In two cases, each time only go down or to the right, then f (m, n) = f (m-1.n) + f (M, n-1 ). recursion is used directly at the beginning, and the timeout is reached. It should exist in the array.

 1 public class Solution { 2     public int uniquePaths(int m, int n) { 3             int[][] f = new int[m][n]; 4             for (int i = 0; i < n; i++) { 5                 f[0][i]=1; 6             } 7              8             for (int i = 0; i < m; i++) { 9                 f[i][0]=1;10             }11             12             for (int i = 1; i < m; i++) {13                 for (int j = 1; j < n; j++) {14                     f[i][j]=f[i-1][j]+f[i][j-1];15                 }16             }17     return f[m-1][n-1];18     }19 }

 

Leetcode unique paths