62. Unique Paths

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?

Above is a 3 x 7 grid. How many possible unique paths are there?

Note: m and n will be at most 100.

题目比较简单，主要学习了下C++二维动态数组的创建.

class Solution {
public:
    int uniquePaths(int m, int n) {
        double **a;
        a = new double*[m]; 
        for(int j=0;j<m;j++)
        {
            a[j] = new double[n];      
        }
        for(int i=0; i<m;i++)
            for(int j=0;j<n;j++)
                a[i][j]=1;

        for(int i=1; i<m;i++)
            for(int j=1;j<n;j++)
                a[i][j]=a[i-1][j]+a[i][j-1];

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

        for (int i=0;i<m;i++)
        {
            delete[] a[i]; //先撤销指针元素所指向的数组
        }                        
        delete[] a; 
    }
};

JAVA代码。

public class Solution {
    public int uniquePaths(int m, int n) {
        int [][] a=new int[m][n];
       for(int i=0; i<m;i++)
            for(int j=0;j<n;j++)
                a[i][j]=1;


        for(int i=1; i<m;i++)
            for(int j=1;j<n;j++)
                a[i][j]=a[i-1][j]+a[i][j-1];

        return a[m-1][n-1];
    }
}