array-permutation.c

gistfile1.c

#include <stdio.h>
#include <stdlib.h> 

void swap(int *a, int *b) 
{
    //printf("%p %p\n", a, b);
    //printf("%d %d\n", *a, *b);
    int tmp = *a; 
    *a = *b; 
    *b = tmp;
    //printf("%d %d\n", *a, *b);

}


void print(int ar[], int size)
{
    int i;
    for (i = 0; i < size; i++) {
        printf("%d ", ar[i]);
    }   
    printf("\n");
}

void f(int *ar, int i, int size)
{
    if (size == i) {
        print(ar, size);
        return;
    }
    int j = i;
    for (j = i; j < size; j++) {
        swap(ar+i, ar+j);
        f(ar, i+1, size);
        swap(ar+i, ar+j);
    }
}

int main(int argc, const char *argv[])
{
    int la[] = {1};
    int lb[] = {1,2};
    int lb[] = {1,2};
    int lc[] = {1,2,3};
    int ld[3][2] = {{1,2},{2,3},{3,4}};

    f(lc, 0, 3);


    return 0;
}

/*
f(int *ar, int i, int size)
ar = 1 2 3
size = 3

f([1 2 3], 0, 3)
	j = 0
	for(j = 0; j < 3; j++)
		swap(ar0,ar0)
		f([1 2 3], 1, 3)
			j = 1
			for(j = 1; j < 3; j++)
				swap(ar1,ar1)
				f([1 2 3], 2, 3)
					j = 2
					for(j = 2; j < 3; j++)
						swap(ar2,ar2)
						f([1 2 3], 3, 3) >>>> 123
						swap(ar2,ar2)
				swap(ar1,ar1)
			for(j = 2; j < 3; j++)
				swap(ar1,ar2)
				f([1 3 2], 2, 3)
					j = 2
					for(j = 2; j < 3; j++)
						swap(ar2,ar2)
						f([2 1 3], 3, 3) >>>> 132
						swap(ar2,ar2)
				swap(ar1,ar2) 1 2 3
		swap(ar0,ar0) 1 2 3
		
	for(j = 1; j < 3; j++)
		swap(ar0,ar1)
		f([2 1 3], 1, 3)
			j = 1
			for(j = 1; j < 3; j++)
				swap(ar1,ar1)
				f([2 1 3], 2, 3)
					j = 2
					for(j = 2; j < 3; j++)
						swap(ar2,ar2)
						f([2 1 3], 3, 3) >>>> 213
						swap(ar2,ar2)
				swap(ar1,ar1)
			for(j = 2; j < 3; j++)
				swap(ar1,ar2)
				f([2 3 1], 2, 3)
					j = 2
					for(j = 2; j < 3; j++)
						swap(ar2,ar2)
						f([2 3 1], 3, 3) >>>> 231
						swap(ar2,ar2)
				swap(ar1,ar2) 2 1 3
		swap(ar0,ar0) 2 1 3
		
	for(j = 2; j < 3; j++)
		swap(ar0,ar2)
		f([3 1 2], 1, 3)
			j = 1
			for(j = 1; j < 3; j++)
				swap(ar1,ar1)
				f([3 1 2], 2, 3)
					j = 2
					for(j = 2; j < 3; j++)
						swap(ar2,ar2)
						f([2 1 3], 3, 3) >>>> 312
						swap(ar2,ar2)
				swap(ar1,ar1)
			for(j = 2; j < 3; j++)
				swap(ar1,ar2)
				f([3 2 1], 2, 3)
					j = 2
					for(j = 2; j < 3; j++)
						swap(ar2,ar2)
						f([3 2 1], 3, 3) >>>> 321
						swap(ar2,ar2)
				swap(ar1,ar2) 1 2 3
		swap(ar0,ar0) 1 2 3
*/