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subsets.cpp
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168 lines (147 loc) · 3.94 KB
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// Source : https://oj.leetcode.com/problems/subsets/
// Author : Hao Chen
// Date : 2014-07-03
/**********************************************************************************
*
* Given a set of distinct integers, S, return all possible subsets.
*
* Note:
*
* Elements in a subset must be in non-descending order.
* The solution set must not contain duplicate subsets.
*
* For example,
* If S = [1,2,3], a solution is:
*
* [
* [3],
* [1],
* [2],
* [1,2,3],
* [1,3],
* [2,3],
* [1,2],
* []
* ]
*
*
**********************************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
void getCombination(vector<int>& v, int n, int k, vector<int>& solution, vector< vector<int> >& result );
vector<vector<int> > combine(vector<int>& v, int k);
vector<vector<int> > combine1(vector<int>& v, int k);
vector<vector<int> > combine2(vector<int>& v, int k);
vector<vector<int> > subsets(vector<int> &S) {
vector<vector<int> > result;
for(int i=0; i<=S.size(); i++){
vector<vector<int> > r = combine(S, i);
result.insert(result.end(), r.begin(), r.end());
}
return result;
}
vector<vector<int> > combine(vector<int>& v, int k) {
if (random()%2){
cout << "recusive method!" << endl;
return combine1(v, k);
}
cout << "non-recusive method!" << endl;
return combine2(v, k);
}
vector<vector<int> > combine1(vector<int> &v, int k) {
vector<vector<int> > result;
vector<int> solution;
getCombination(v, v.size(), k, solution, result);
return result;
}
void getCombination(vector<int> &v, int n, int k, vector<int>& solution, vector< vector<int> >& result ){
if (k==0){
//sort to meet LeetCode requirement
vector<int> v = solution;
sort(v.begin(), v.end());
result.push_back(v);
return;
}
for(int i=n; i>0; i--){
solution.push_back(v[i-1]);
getCombination(v, i-1, k-1, solution, result);
solution.pop_back();
}
}
vector<vector<int> > combine2(vector<int> &v, int k) {
vector<vector<int> > result;
vector<int> d;
int n = v.size();
for (int i=0; i<n; i++){
d.push_back( (i<k) ? 1 : 0 );
}
//1) from the left, find the [1,0] pattern, change it to [0,1]
//2) move all of the 1 before the pattern to the most left side
//3) check all of 1 move to the right
while(1){
vector<int> tmp;
for(int x=0; x<n; x++){
if (d[x]) tmp.push_back(v[x]);
}
sort(tmp.begin(), tmp.end());
result.push_back(tmp);
//step 1), find [1,0] pattern
int i;
bool found = false;
int ones =0;
for(i=0; i<n-1; i++){
if (d[i]==1 && d[i+1]==0){
d[i]=0; d[i+1]=1;
found = true;
//step 2) move all of right 1 to the most left side
for (int j=0; j<i; j++){
d[j]=( ones > 0 ) ? 1 : 0;
ones--;
}
break;
}
if (d[i]==1) ones++;
}
if (!found){
break;
}
}
return result;
}
void printResult(vector<vector<int> >& result)
{
for(int i=0; i<result.size(); i++){
cout << "{";
for(int j=0; j<result[i].size(); j++){
cout << " " << result[i][j];
}
cout << " }" <<endl;
}
}
void printArray(vector<int>& v){
cout << "{";
for(int i=0; i<v.size(); i++) {
cout << " " << v[i];
}
cout << " }" << endl;
}
int main(int argc, char** argv)
{
srand(time(NULL));
int n = 3;
if (argc>1){
n = atoi(argv[1]);
}
vector<int> v;
for(int i=n; i>0; i--){
v.push_back(i);
}
printArray(v);
vector<vector<int> > r = subsets(v);
printResult(r);
}