A robot is located at the top-left corner of a m x n grid (marked ‘Start‘ in the diagram 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 diagram below).
How many possible unique paths are there?
解题思路一：
BigInteger，JAVA实现如下：
import java.math.BigInteger;
public class Solution {
public int uniquePaths(int m, int n) {
if (n > m) {
int temp = n;
n = m;
m = temp;
}
return Amn(m + n - 2, n - 1).divide(factorial(n - 1)).intValue();
}
static BigInteger Amn(int m, int n) {
if (n == 0)
return BigInteger.valueOf(1);
if (n == 1)
return BigInteger.valueOf(m);
else
return Amn(m - 1, n - 1).multiply(BigInteger.valueOf(m));
}
static BigInteger factorial(int n) {
if (n == 1 || n == 0)
return BigInteger.valueOf(1);
else
return factorial(n - 1).multiply(BigInteger.valueOf(n));
}
}
Java for LeetCode 062 Unique Paths
原文：http://www.cnblogs.com/tonyluis/p/4506913.html