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

typedef struct exp {
char op;
char *term;
struct exp *left;
struct exp *right;
} Exp;

Exp *make_exp2(char *str){
if(!str || !*str) return NULL;//*str == '\0' is format error.
char *mul = strrchr(str, '*');
char *div = strrchr(str, '/');
Exp *node = malloc(sizeof(*node));
if(mul == NULL && div == NULL){
node->op = '\0';
node->term = str;
node->left = node->right = NULL;
return node;
}
char *op;
op = mul < div ? div : mul;
node->op = *op;
*op = '\0';
node->left = make_exp2(str );
node->right = make_exp2(op+1);
return node;
}

Exp *make_exp(char *str){
if(!str || !*str) return NULL;//*str == '\0' is format error.
char *minus = strrchr(str, '-');
char *plus = strrchr(str, '+');
if(minus == NULL && plus == NULL)
return make_exp2(str);
char *op;
Exp *node = malloc(sizeof(*node));
op = minus < plus ? plus : minus;
node->op = *op;
*op = '\0';
node->left = make_exp(str );
node->right = make_exp(op+1);
return node;
}

float print(Exp *exp, int level){
int i;
float val = 0;
if(exp->op){

for(i=0;i<level;++i)
printf(" ");

printf("%c\n", exp->op);

for(i=0;i<level;++i)
printf(" ");

if (exp->op == '+'){
val += print(exp->right, level+1);
} else
if (exp->op == '-'){
val -= print(exp->right, level+1);
} else
if (exp->op == '*'){
val = 1;
val *= print(exp->right, level+1);
}

printf("\n");

for(i=0;i<level;++i)
printf(" ");

if (exp->op == '+' || exp->op == '-'){
val += print(exp->left, level+1);
} else
if (exp->op == '*'){
val *= print(exp->left, level+1);
}

printf("\n");
} else {
for(i=0;i<level;++i)
printf(" ");

val = atof(exp->term);
printf("%s\n", exp->term);
}
return val;
}

int main(void) {
char str[100];

printf("Enter a value :");
gets(str);

Exp *exp = make_exp(str);

printf("%f", print(exp, 0));

return 0;
}