Understanding the CMP in Qsort

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Just stick it out, okay?

Comparpointer to a function, compares, and elements.
This function was called repeatedly by to qsort compare and elements. It shall follow the following prototype:

int compar (constvoidconstvoid* p2);

Taking pointers as arguments (both converted to const void*). The function defines the order of the elements by returning (in a stable and transitive manner):

return value	meaning
<0	The element pointed by p1 goes before the element pointed byp2
0	The element pointed by was equivalent to the p1 element pointed byp2
>0	The element pointed by p1 goes after the element pointed byp2

If you want to sort the array in ascending order, you need to handle two parameters P1, P2, if P1 > P2, then the CMP needs to return a <0 value, so it is P1-P2

If P1<P2, then the CMP needs to return a value of >0, so the same is P1-P2, no contradiction at all.

If you want to sort the array in descending order, you need to handle two parameters P1, P2, if P1 > P2, the sort should be P1 in front of P2, that CMP needs to return a <0 value, so is P2-P1, if P1<P2, then CMP needs to return a >0 value, So it's the same p2-p1.

Understanding the CMP in Qsort