C (GCC), 63 60 bytes

-3 bytes thanks to @Juan Ignacio Díaz

f(v,n,b,j)int*v;{for(b=j=0;n+~j;)b|=v[j/2]<v[++j];return!b;}

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Original note of the 63 bytes version:

I know 2 bytes can be saved by inverting the meaning of the values 0 and 1, but I prefer to keep it this way.