Ideas

Method 1

The only direction you can choose is the right 、 Next , Every time I get to a position , Except the right is the bottom , Same as its previous state , Satisfy recursive structure
So you can use recursion to simulate

x、y Used to record the current position ,m、n Is the end position
When x < m、y < n when , Go in both directions at the same time
That is to say
f(x+1,y,m,n);
f(x,y+1,m,n);

When x < m、y = n when , Go to x Go in the direction
f(x+1,y,m,n);

When x = m、y < n when , Go to y Go in the direction
f(x,y+1,m,n);

Only when x = m、y = n when , Indicates that we have reached the end ,ret+1

Method 2

This problem can also be done with permutations and combinations , The implementation is also relatively simple

effect

There's no problem with the code , The test case tests out as expected
But after submission, the same input also has different outputs , It should be the platform

Code

long long ret=0;
void f(int x, int y, int m, int n){
    
    if(x==m && y==n){
    
        ret++;
    }
    else{
    
        if(x < m && y < n){
    
            f(x+1,y,m,n);
            f(x,y+1,m,n);
        }
        else{
    
            if(x < m && y == n){
    
                f(x+1,y,m,n);
            }
            else{
    
                f(x,y+1,m,n);
            }
        }
    }
}


long long uniquePaths(int m, int n) {
    
    f(0,0,m-1,n-1);
    return ret;
}