Listing 1

#include <stdio.h>

#define NULL_IDX 0

typedef struct {
       char value;
       size_t left_child;
       size_t right_child;
} Node;

static Node tree[] = {
       {' ',  NULL_IDX, NULL_IDX},    /* [0] */
       {'*',        2,        3},     /* [1] */
       {'+',        4,        5},     /* [2] */
       {'-',        6,        7},     /* [3] */
       {'A', NULL_IDX, NULL_IDX},     /* [4] */
       {'B', NULL_IDX, NULL_IDX},     /* [5] */
       {'C', NULL_IDX, NULL_IDX},     /* [6] */
       {'/',        8,        9},     /* [7] */
       {'D', NULL_IDX, NULL_IDX},     /* [8] */
       {'E', NULL_IDX, NULL_IDX}      /* [9] */
};

static size_t root = 1;

/* End of File */