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Excerpt
When we implement add function by operator +

...

in C++, sometimes we face over error - actually system does not show any error and that should be continuously increased, but there is a possibility to change into minus value suddenly.

You can see the same case when you compile and run by below code:

Code Block

language	cpp
title	test.cpp

#include <iostream>
using namespace std;

int main()
{
        int a;
        for(int b=0; b<1000000; b++) {
                cout << a << "\n";
                a+= 10000000;#include<stdio.h> 
#include<limits.h> 
#include<stdlib.h> 
  
int addOvf(int* result, int a, int b) 
{ 
   if( a > INT_MAX - b) 
     return -1; 
   else
   { 
     *result = a + b; 
      return 0; }
}

Below safe_add() function enables you to check overflow error:

Code Block

language	cpp
title	safe_add.cpp

#define INT_MAX  } 
} 
  
int main() 
{ 
  int *res = (int *)malloc(sizeof(int)); 
  int x = 2147483640; 
  int y = 10; 
  
  printf("%d", addOvf(res, x, y)); 
  printf("\n %d", *res); 
  getchar(); 
  return 0; 
} 2147483647
#define INT_MIN -2147483648

    int safe_add(int &sum, int a, int b) {
        if (abs(a)>INT_MAX-abs(b)) {
            cout << "overflow : " << a << "+" << b << endl;
            return 0;
        }
        
        sum = a + b;
        
        return 1;
    }

Time Complexity : O(1)
Space Complexity: O(1)

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