Merge 2 sorted array without extra space

def nextGap(t):
    if (t <= 1):
        return 0
    
    return (t//2) + (t%2)
        
def merge(arr1,arr2,n,m):
    gap=n+m
    gap=nextGap(gap)
    while(gap > 0):
        i=0
        while(i+gap < n):
            if(arr1[i] > arr1[i+gap]):
                arr1[i],arr1[i+gap]=arr1[i+gap],arr1[i]
            i+=1
            
        j=gap-n if gap > n else 0
        while(i < n and j < m):
            if (arr1[i] > arr2[j]):
                arr1[i],arr2[j]=arr2[j],arr1[i]
                
            i+=1
            j+=1
            
        if (j < m):
            j=0
            while(j+gap < m):
                if (arr2[j] > arr2[j+gap]):
                    arr2[j],arr2[j+gap]=arr2[j+gap],arr2[j]

                j+=1
                
        gap=nextGap(gap)
        
       
arr1=[1,4,7,8,9]
arr2=[2,3,9]
n=len(arr1)
m=len(arr2)
merge(arr1,arr2,n,m)
for i in range(n):
    print(arr1[i],end=" ")
print()
for i in range(m):
    print(arr2[i],end=" ")
print()