Count all possible paths from top left to bottom right of a mXn matrix

PROBLEM :

Given a M X N matrix with initial position at top-left corner, find the number of possible unique paths to reach the bottom right corner of the grid from the initial position.


NOTE: Possible moves can be either down or right at any point in time, i.e., we can move to matrix[i+1][j] or matrix[i][j+1] from matrix[i][j].


Input:

The first line contains an integer T, depicting total number of test cases.
Then following T lines contains an two integers A and B depicting the size of the grid.

Output:

Print the number of unique paths to reach bottom-right corner from the top-left corner.


Constraints:

1 = T = 30
1 = M = 15
1 = N = 15

Example:

Input
2
2 2
3 4
Output
2
10

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SIMPLE c++ IMPLEMENTATION :
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#include<iostream>
using namespace std;
int Number_of_Unique_Paths(int ,int ) ;
int main()
 {
int t,m,n,no ;
cin>>t ;
while(t--)
{
   cin>>m>>n ;
   no=Number_of_Unique_Paths(m,n) ;
   cout<<no<<endl ;
}
return 0;
}

int Number_of_Unique_Paths(int m,int n)
{
    int mat[m][n] ;
    int i,j ;
   
    for(i=0;i<n;i++)
        mat[0][i]=1 ;
   
    for(j=0;j<m;j++)
        mat[j][0]=1 ;
       
    for(i=1;i<m;i++)
    {
        for(j=1;j<n;j++)
            mat[i][j]=mat[i-1][j]+mat[i][j-1] ;
    }
    return mat[m-1][n-1] ;
}

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