[Classic algorithm] permutation combination-full sort

Title Description:

Arrange a set of numbers, letters, or symbols to get a different combination order, for example 1 2 3 the full array of three numbers are: 1 2 3, 1 3 2, 2 1 3, 2 3 1, 3 1 2, 3 2 1.

Topic Analysis:

Set Number of P = {r1, r2, R3, ..., RN}, all arranged as Perm (p), pn = P–{rn}.

Then perm (p) = R1perm (p1), R2perm (P2), r3perm (P3), ..., Rnperm (PN). When n = 1 o'clock perm (P} = r1.

such as: all permutations of {1, 2, 3, 4, 5}

1, first look at the last two number 4, 5. Their full arrangement is 4 5 and 5 4, which is the full arrangement of 4 starting with 5 and the full arrangement of 5 beginning with 4.

Because the whole arrangement of a number is itself, the above results are obtained.

2, then look after three number 3, 4, 5. They are all arranged in 3 4 5, 3 5 4, 4 3 5, 4 5 3, 5 3 4, 5 4 36 group numbers.

That is, a fully arranged combination of 3 and 4,5, a fully arranged combination of 4-beginning and 3,5, and a full-aligned set of 5-and 3,4-prefaced.

Program code:

#include <gtest/gtest.h>using namespacestd;//Full arrangementvoidSwap (int* V1,int*v2) {    if(V1 = =v2)return; intValue = *v1; *V1 = *v2; *v2 =value;}voidShowresult (intData[],intSizeintcount) {     for(inti =0; i < size; ++i) {cout<< Data[i] <<" "; }    if(Count%8==0) {cout<<Endl; }    Else{cout<<"  "; }}voidPermutation (intData[],intBeginintEndint&count) {        if(Begin <end) {         for(inti = begin; I < end; ++i) {Swap (&data[begin], &Data[i]); Permutation (data, begin+1, end, count); Swap (&data[begin], &Data[i]); }    }    Else    {        ++count;    Showresult (data, end, count); }}test (Algo, tpermutation) {intData[] = {1,2,3,4}; intNcount =0; //4 Numbers 4! = FivePermutation (data,0,4, ncount); Assert_eq (Ncount, -); //5 Numbers 5! = +    intData1[] = {1,2,3,4,5}; Ncount=0; Permutation (data1,0,5, ncount); Assert_eq (Ncount, -); //6 Numbers 6! = 720    intData2[] = {1,2,3,4,5,6}; Ncount=0; Permutation (data2,0,6, ncount); Assert_eq (Ncount,720);}

[Classic algorithm] permutation combination-full sort