Remove the last element inside an array - c

Question

My problem: I do not know how to delete the last element entered inside the array. The program should stop when the user enters a negative number and should not include the negative number inside the array. I tried, but I cant find the solution. This is my Code:
int main () {
float array[20];
float max ,min;
float rem;
int i;
char op;
for (i = 0; i <= 20; i++){
printf("Enter the element inside array[%d]: ",i);
scanf("%f", &array[i]);
if (array[i] < 0)
break;
}
printf("Enter ......: ");
scanf("%s", &op);
switch (op){
case 'h':
max = array[0];
for (i = 0; i < 20; i++){
if (max < array[i]){
max = array[i];
}
}
printf("The biggest number is: %f\n", max);
break;
case 'l':
min = array[0];
for (i = 0; i < 20; i++){
if (min > array[i]){
min = array[i];
}
}
printf("The smallest number is: %f\n", min);
break;
}
return 0;
}
Please help , I run out of ideas.
Thank you very much.

Answer 1

Simply check entered value before storing in array:
int main () {
float array[20]={0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
float max ,min;
float rem;
int i;
float a;
char op;
for (i = 0; i < 20; i++){
printf("Enter the element inside array[%d]: ",i);
scanf("%f", &a);
if (a < 0)
break;
array[i]=a;
}

Answer 2

i am sorry for my last answer but this is true ;)
#include<stdio.h>
int length(const float *array) {
int count = 0;
while(array[count]) count++;
return count;
}
void main () {
float array[20];
float max ,min;
float rem,input;
int i;
char op;
int length = 0;
for (i = 0; i < 20; i++){
printf("Enter the element inside array[%d]: ",i);
scanf("%f", &input);
if (input < 0)
break;
length++;
array[i] = input;
}
printf("Enter ......: ");
scanf(" %c", &op);
switch (op){
case 'h':
max = array[0];
for (i = 0; i < 20; i++){
if (max < array[i]){
max = array[i];
}
}
printf("The biggest number is: %f\n", max);
break;
case 'l':
min = array[0];
for (i = 0; i < length; ++i){
if (min > array[i]){
min = array[i];
}
}
printf("The smallest number is: %f\n", min);
break;
}
system("pause");
}

Answer 3

Use a temporary variable before , if it is positive store in array , if not take necessary actions.
for (i = 0; i < 20; i++){
printf("Enter the element inside array[%d]: ",i);
scanf("%f", &x) // declare x as float x;
if (x< 0) // if negative break
break;
array[i]=x; // store into array
}
And also some problems in your program -
printf("Enter ......: ");
scanf("%s", &op); // op is char variable use %c specifier
^ use instead %c
Write like this instead-
scanf(" %c", &op);
this first loop access index out of bound causing UB
for (i = 0;i<=20; i++){ // change condition to i<20 (index can go from 0 to 19)
//your code // as array is declared as float array[20]
}
Both the loops for max and min can go like this -
for (i= 0;array[i]; i++){ // no need to keep track of length of array
Click on link to see working code.