A simple java implementation, refer to c++ std::next_permutation:
public static void main(String[] args){
int[] list = {1,2,3,4,5};
List<List<Integer>> output = new Main().permute(list);
for(List result: output){
System.out.println(result);
}
}
public List<List<Integer>> permute(int[] nums) {
List<List<Integer>> list = new ArrayList<List<Integer>>();
int size = factorial(nums.length);
// add the original one to the list
List<Integer> seq = new ArrayList<Integer>();
for(int a:nums){
seq.add(a);
}
list.add(seq);
// generate the next and next permutation and add them to list
for(int i = 0;i < size - 1;i++){
seq = new ArrayList<Integer>();
nextPermutation(nums);
for(int a:nums){
seq.add(a);
}
list.add(seq);
}
return list;
}
int factorial(int n){
return (n==1)?1:n*factorial(n-1);
}
void nextPermutation(int[] nums){
int i = nums.length -1; // start from the end
while(i > 0 && nums[i-1] >= nums[i]){
i--;
}
if(i==0){
reverse(nums,0,nums.length -1 );
}else{
// found the first one not in order
int j = i;
// found just bigger one
while(j < nums.length && nums[j] > nums[i-1]){
j++;
}
//swap(nums[i-1],nums[j-1]);
int tmp = nums[i-1];
nums[i-1] = nums[j-1];
nums[j-1] = tmp;
reverse(nums,i,nums.length-1);
}
}
// reverse the sequence
void reverse(int[] arr,int start, int end){
int tmp;
for(int i = 0; i <= (end - start)/2; i++ ){
tmp = arr[start + i];
arr[start + i] = arr[end - i];
arr[end - i ] = tmp;
}
}