/**
 * 算法思想：
 * 经典回溯算法，递归返回的条件为临时栈中的元素个数为k个；
 *
 *
 *
 *
 **/

void rec(int n, int k, int index, int *stack, int *stack_index, int *ret_index, int **ret){
    if(*stack_index == k){
        ret[*ret_index] = (int *)malloc(sizeof(int) * k);
        memcpy(ret[*ret_index], stack, sizeof(int) * k);
        (*ret_index)++;
        return;
    }
    
    for(; index<=n; index++){
        stack[(*stack_index)++] = index;
        
        rec(n, k, index+1, stack, stack_index, ret_index, ret);
        
        (*stack_index)--;
    }
}

#define LEN 0xfffff

int** combine(int n, int k, int* rs, int** colsize){
    int **ret = (int **)malloc(sizeof(int *) * LEN);
    int *stack = (int *)malloc(sizeof(int) * LEN);
    int stack_index = 0;
    int *cs = (int *)malloc(sizeof(int) * LEN);
    
    int ret_index = 0;
    
    rec(n, k, 1, stack, &stack_index, &ret_index, ret);
    
    *colsize = cs;
    
    int i;
    for(i=0; i<ret_index; i++){
        cs[i] = k;
    }
    printf("ret_index = %d\n", ret_index);
    *rs = ret_index;
    return ret;
}