codegolf interleave

# !/usr/bin/python3

#https://codegolf.stackexchange.com/questions/123459/interleave-numbers-from-1-to-n-with-the-same-numbers-reversed

# c 1
# m;i(n){for(m=n;m--;)printf("%d%d",n-m,m+1);}

# int main() {
#     i(4);
# }

# python
# i=lambda n:"".join("%s"*2%(i+1,n-i)for i in range(n))  
# i=lambda n:"".join(map(lambda i:"%s"*2%(i+1,n-i),range(n)))
# i=lambda n:"".join(`i+1`+`n-i`for i in range(n)) 

# js
# i=n=>{r="";for(i=n;i--;){r+=n-i;r+=i+1}return r}
# console.log(i(4))