1、构造 + 回溯法(输出字典序)
void print(){ int i; for (i = 1; i <= n; i++) cout << consist[i] << ' '; cout << endl; } void dfs(int k){//深搜函数,当前是第k格 int i; if (k == n) {//填满了的时候 print();//输出当前解 return; } for (i = 1; i <= n; i++){//1-n循环填数 if (!fuck[i]){//如果当前数没有用过 fuck[i] = 1;//标记一下 consist[k + 1] = i;//把这个数填入数组 dfs(k + 1);//填下一个 fuck[i] = 0;//回溯 } } }
2、深搜(输出字典序)
#include <iostream> #include <stdio.h> #include <vector> using namespace std; int N; vector<int> arr; void dfs(vector<int>ans, int k) { if (k == N) { for (int i = 0; i < N; i++) { cout << ans[i] << ' '; } cout << endl; return; } for (int i = k; i < N; i++) { swap(ans[i], ans[k]); dfs(ans, k + 1); } } int main() { cin >> N; for (int i = 0; i < N; i++) { arr.push_back(i + 1); } dfs(arr, 0); return 0; }
3、还是深搜(非字典序)
这个输出出来,不是字典序,是一种很古怪的顺序。
#include <iostream> #include <fstream> using namespace std; int arr[10]; void process(int k,int n) { if (k == n) { for (int i = 1; i <= n; i++) { cout << arr[i] << ' '; } cout << endl; return; } for (int i = k; i <= n; i++) { swap(arr[i], arr[k]); process(k + 1, n); swap(arr[i], arr[k]); } } int main() { fstream fin("data.in"); int n; fin >> n; for (int i = 1; i <= n; i++) { arr[i] = i; } process(1,n); }
4、C++ algoritgm next_permutation(输出字典序)
#include <iostream> #include <algorithm> #include <fstream> using namespace std; int arr[10]; int main() { fstream fin("data.in"); int n; fin >> n; for (int i = 1; i <= n; i++) { arr[i] = i; } while (next_permutation(arr + 1, arr + n + 1)) { for (int i = 1; i <= n; i++) { cout << arr[i] << ' '; } cout << endl; } }