LeetCode：62.63不同路徑問題。

不同路徑問題：

62.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 7 x 3 grid. How many possible unique paths are there?

Note: m and n will be at most 100.

Example 1:

Input: m = 3, n = 2
Output: 3
Explanation:
From the top-left corner, there are a total of 3 ways to reach the bottom-right corner:
1. Right -> Right -> Down
2. Right -> Down -> Right
3. Down -> Right -> Right

Example 2:

Input: m = 7, n = 3
Output: 28

---

class Solution {
public:
    int uniquePaths(int m, int n) {
        if(m==1&&n==1)
            return 1;
        int** p=new int* [m];
        for(int i=0;i<m;i++)
            p[i]=new int[n];
        p[0][0]=0;
        for(int i=1;i<m;i++)
            p[i][0]=1;
        for(int j=1;j<n;j++)
            p[0][j]=1;
        for(int i=1;i<m;i++)
            for(int j=1;j<n;j++)
            {
                p[i][j]=p[i][j-1]+p[i-1][j];
            }
        return p[m-1][n-1];
    }
};

構建遞歸關係的時候，注意考慮遞歸出口。

提交問題是遇到報錯reference binding to null pointer of type 'value_type'，原因vector嵌套時沒有初始化大小，下標訪問越界。

參考鏈接：https://blog.csdn.net/m0_38088298/article/details/79249044