Effective Stack Implementation in C

Question

https://www.hackerrank.com/challenges/equal-stacks
For this problem, I tried to implement a stack data structure in c. But I get a timeout for some cases using the following code:

#include <math.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <assert.h>
#include <limits.h>
#include <stdbool.h>
struct Stack{
    int top;
    int size;
    int sum;
    int* arr;
};
struct Stack* createStack(int size){
    struct Stack* stack = (struct Stack*)malloc(sizeof(struct Stack));
    stack->size=size;
    stack->top=-1;
    stack->sum=0;
    stack->arr = (int*)malloc(sizeof(int)*size);
    return stack;
}
int isempty(struct Stack* stack){
    if(stack->top==-1)
        return 1;
    return 0;
}
void push(struct Stack* stack,int term){
    stack->top++;
    stack->arr[stack->top]=term;
    stack->sum+=term;
}
void pop(struct Stack* stack){
    if(isempty(stack)==0){
        stack->sum-=stack->arr[stack->top];
        stack->top--;
    }
}
int main(){
    int size1,size2,size3;
    scanf("%d %d %d",&size1,&size2,&size3);
    int arr1[size1];
    for(int i=0;i<size1;i++)
        scanf("%d",&arr1[i]);
    struct Stack* stack1 = createStack(size1);
    for(int i=size1-1;i>=0;i--)
        push(stack1,arr1[i]);
    int arr2[size2];
    for(int i=0;i<size2;i++)
        scanf("%d",&arr2[i]);
    struct Stack* stack2 = createStack(size2);
    for(int i=size2-1;i>=0;i--)
        push(stack2,arr2[i]);
    int arr3[size3];
    for(int i=0;i<size3;i++)
        scanf("%d",&arr3[i]);
    struct Stack* stack3 = createStack(size3);
    for(int i=size3-1;i>=0;i--)
        push(stack3,arr3[i]);
    while(stack1->sum!=stack2->sum || stack2->sum!=stack3->sum){
        if(stack1->sum > stack2->sum && stack1->sum > stack3->sum)
            pop(stack1);
        if(stack2->sum > stack1->sum && stack2->sum > stack3->sum)
            pop(stack2);
        if(stack3->sum > stack2->sum && stack3->sum > stack1->sum)
            pop(stack3);
    }
    printf("%d\n",stack1->sum);
}

Can anyone suggest a better approach using only the stack data structure (preferably in C)?

Answer 1

The reason you could exceed the time limit is because the while loop never ends if

a) . , while, , .

b) , 20, 10, 10, , ?

Answer 2

, , , , .

:

struct Stack *high = (stack1->sum > stack2->sum) ? stack1 : stack2;
struct Stack *low  = (high == stack1) ? stack2 : stack1;

if ( stack3->sum > high->sum )
    high = stack3;
else if ( stack3->sum < low->sum )
    low = stack3;

:

while ( high->sum > low->sum )
    pop( high );