# 3 of basic sorting algorithms -- quick sorting

Source: Internet
Author: User

The idea of fast sorting is not mentioned. The central axis group uses a temporary unit. Time complexity O (nlogn ). The following is an implementation:

# Include <iostream> using namespace STD; Template <typename T> bool _ less (t a, t B) {return a <B ;}template <typename t, typename F> void qsort (t a [], int N, f = _ Less <t>) {If (n <2) return; int first = 0, last = n-1; t temp = A [0]; while (first! = Last) {While (first! = Last &&! F (a [last], temp) last --; A [first] = A [last]; while (first! = Last & F (a [first], temp) First ++; A [last] = A [first];} A [first] = temp; qsort (, first, f); qsort (a + last + 1, n-last-1, f);} template <typename T> void show (t a [], int N) {for (INT I = 0; I <n; ++ I) {cout <A [I] <'';}cout <Endl ;}int main () {float a [] = {3.22, 4.6, 1.27, 9.81, 5.5, 0.12, 2.75, 6.7, 7.01}; qsort (A, 10, _ Less <float>); show (A, 10); Return 0 ;}

Notes:

1. The template class supports default template parameters. Template functions or member template functions do not support the default template parameters (the sort in STL supports the third parameter by reloading the two functions! Instead of using the default template parameters !!)

2. Do not write type parameters for template function calls. The Compiler automatically deduce them.

3. The key to recursion is whether the boundary condition is fully considered.

4. Reference Table: it is incorrect to select the first element as the center. Median of three partitioning is commonly used )!! Is to take the center value of a [first], a [last], a [(first + last)/2.

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