#include <stdio.h>

long long mdc(long long n1, long long n2) {
    while (n2 != 0) {
        long long temp = n2;
        n2 = n1 % n2;
        n1 = temp;
    }
    return n1;
}

long long inverso(long long n1, long long m) {
    for (int i = 1; i < m; i++){
        if((n1*i)% m == 1){
            return i;
        }
    }
    return -1;
}


long long teoremaChinesDoResto(int n, long long n1[], long long m[]) {
    long long M = 1;
    for (int i = 0; i < n; i++) {
        M *= m[i];
    }
    long long x = 0;

    for (int j = 0; j < n; j++){
        if (mdc(n1[j], m[j]) != 1){
            printf("\n\nOs modulos nao sao coprimos. Nao e possivel realizar o Teorema Chines do Resto\n");
            return -1;
        }
    }

    for (int i = 0; i < n; i++) { 
        long long Mi = M / m[i];
        long long inv = inverso(Mi, m[i]);
        x += n1[i] * Mi * inv;
    }
    return x % M;
}

int main() {
    int n;
    printf("Numero de equacoes (ate 4): ");
    scanf("%d", &n);

    if (n < 1 || n > 4) {
        printf("Numero invalido. Deve ser entre 1 e 4.\n");
        return 1;
    }
    printf("\nVoce esta resolvendo o sistema de congruencias do tipo:\n");
    for (int i = 0; i < n; i++) 
        printf("x = a[%d] (mod m[%d])\n", i + 1, i + 1);

    long long a[4], m[4];
    
    for (int i = 0; i < n; i++) {
        printf("\nDigite o valor de a[%d]: ", i + 1);
        scanf("%lld", &a[i]);
        printf("Digite o valor de m[%d]: ", i + 1);
        scanf("%lld", &m[i]);
    }
    long long resultado = teoremaChinesDoResto(n, a, m);
    if (resultado == -1) return 1;
    long long M = 1;
    for (int i = 0; i < n; i++) 
        M *= m[i];
        
    printf("\n\nSolucao do sistema: x = %lld (mod %lld)\n", resultado, M);

    return 0;
}
by

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Read inputs from stdin

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#include <stdio.h>
int main()
{
    char name[50];
    printf("Enter name:");
    scanf("%s", name);
    printf("Hello %s \n" , name );
    return 0;
    
}

About C

C language is one of the most popular general-purpose programming language developed by Dennis Ritchie at Bell laboratories for UNIX operating system. The initial release of C Language was in the year 1972. Most of the desktop operating systems are written in C Language.

Key features:

  • Structured Programming
  • Popular system programming language
  • UNIX, MySQL and Oracle are completely written in C.
  • Supports variety of platforms
  • Efficient and also handle low-level activities.
  • As fast as assembly language and hence used as system development language.

Syntax help

Loops

1. If-Else:

When ever you want to perform a set of operations based on a condition if-else is used.

if(conditional-expression) {
   // code
} else {
   // code
}

You can also use if-else for nested Ifs and if-else-if ladder when multiple conditions are to be performed on a single variable.

2. Switch:

Switch is an alternative to if-else-if ladder.

switch(conditional-expression) {    
case value1:    
 // code    
 break;  // optional  
case value2:    
 // code    
 break;  // optional  
...    
    
default:     
 // code to be executed when all the above cases are not matched;    
}

3. For:

For loop is used to iterate a set of statements based on a condition.

for(Initialization; Condition; Increment/decrement){  
  // code  
}

4. While:

While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.

while(condition) {  
 // code 
}

5. Do-While:

Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.

do {
  // code 
} while (condition);

Arrays

Array is a collection of similar data which is stored in continuous memory addresses. Array values can be fetched using index. Index starts from 0 to size-1.

Syntax

One dimentional Array:

data-type array-name[size];

Two dimensional array:

data-type array-name[size][size];

Functions

Function is a sub-routine which contains set of statements. Usually functions are written when multiple calls are required to same set of statements which increases re-usuability and modularity.

Two types of functions are present in C

  1. Library Functions:

Library functions are the in-built functions which are declared in header files like printf(),scanf(),puts(),gets() etc.,

  1. User defined functions:

User defined functions are the ones which are written by the programmer based on the requirement.

How to declare a Function

return_type function_name(parameters);

How to call a Function

function_name (parameters)

How to define a Function

return_type function_name(parameters) {  
  //code
}