C -- full Arrangement Implementation (recursive method) can be understood by fools

Assume that the array contains n elements, extract each element in the array as a Header element, and then arrange all elements except the first element in the array, in this way, all elements in the array are arranged in full order. [This sentence is the focus !] For example, the full arrangement of and 3 is the full arrangement starting with and 3, respectively. The full arrangement starting with 1 is the full arrangement of 2, 3, and (2, 3) is the full arrangement starting with 2 and 3, respectively. R (n1, n2, n3.... nn) can be simplified to n1, n2, n3 ...... Start with a full arrangement. That is, n1R1 (n2, n3.... nn), n2R2 (n1, n3.... nn), n3R3 (n1, n2,... nn )...... NnR (n1, n2, n3....) Where R1 (n2, n3.... nn) can continue in R mode ...... And so on. Copy the Code # include <iostream> using namespace std; // index, which indicates the position of the subseries in the original series during recursion. // For example, a [] = {1, 2, 3 }, the LENGTH of the original sequence is 3, // If you recursion to a certain step, index = 1, num = 2, which indicates that the following table of the original sequence is 1, the LENGTH starts from 2 (that is, from the sequence 2 and 3), and the full arrangement of the subsequence/(2 and 3) is the LENGTH of the original array. This will not change. Void permutation (int values [], int index, int num, int LENGTH) {int I = 0; if (num = 0) // a full arrangement has been found, show output {for (I = 0; I <LENGTH; ++ I) {cout <values [I] <"" ;}cout <endl; return ;} for (I = 0; I <num; I ++) {swap (values [index + I], values [index]); // The number of the index and the number of the index + I are exchanged to ensure that the first element of the Self-series is exchanged and arranged with each element in the sub-series. Permutation (values, index + 1, num-1); // swap (values [index], values [index + I]); // The inverse operation of the first statement in the for loop, the purpose of which is to make the array look back, // The purpose of doing so is that the arrangement will not produce duplicate results.} Return;} int main () {int values [] = {, 5}; permutation (values, 3); cout <endl; for (int I = 0; I <3; ++ I) {cout <values [I] <'';} cout <endl; return 0;} copy the code