#include <stdio.h>

//No STDIN, digite os coeficientes das 3 equacoes e os termos independentes, linha por linha.
//Cada equacao tem 3 coeficientes (x, y, z) e 1 termo independente (lado direito da igualdade).
//
//Exemplo do sistema:
//2x + 3y - 1z = 5
//1x - 2y + 4z = -3
//3x + 0y + 2z = 4
//
//Digite:
//2
//3
//-1
//1
//-2
//4
//3
//0
//2
//5
//-3
//4

int main() {
    float a[3][3];
    float b[3];
    float det, detX, detY, detZ;
    float x, y, z;

    printf("Digite os coeficientes da matriz A (3x3):\n");
    for (int i = 0; i < 3; i++) {
        for (int j = 0; j < 3; j++) {
            printf("Elemento %d%d: ", i + 1, j + 1);
            while (scanf("%f", &a[i][j]) != 1) {
                while (getchar() != '\n');
                printf("Entrada invalida. Digite novamente o elemento %d%d: ", i + 1, j + 1);
            }
        }
    }

    printf("Digite os termos independentes (vetor B):\n");
    for (int i = 0; i < 3; i++) {
        printf("Elemento %d1: ", i + 1);
        while (scanf("%f", &b[i]) != 1) {
            while (getchar() != '\n');
            printf("Entrada invalida. Digite novamente o elemento %d1: ", i + 1);
        }
    }

    det = a[0][0]*(a[1][1]*a[2][2] - a[1][2]*a[2][1])
        - a[0][1]*(a[1][0]*a[2][2] - a[1][2]*a[2][0])
        + a[0][2]*(a[1][0]*a[2][1] - a[1][1]*a[2][0]);

    if (det == 0) {
        printf("Sistema sem solucao unica\n");
        return 0;
    }

    detX = b[0]*(a[1][1]*a[2][2] - a[1][2]*a[2][1])
         - a[0][1]*(b[1]*a[2][2] - a[1][2]*b[2])
         + a[0][2]*(b[1]*a[2][1] - a[1][1]*b[2]);

    detY = a[0][0]*(b[1]*a[2][2] - a[1][2]*b[2])
         - b[0]*(a[1][0]*a[2][2] - a[1][2]*a[2][0])
         + a[0][2]*(a[1][0]*b[2] - b[1]*a[2][0]);

    detZ = a[0][0]*(a[1][1]*b[2] - b[1]*a[2][1])
         - a[0][1]*(a[1][0]*b[2] - b[1]*a[2][0])
         + b[0]*(a[1][0]*a[2][1] - a[1][1]*a[2][0]);

    x = detX / det;
    y = detY / det;
    z = detZ / det;

    printf("Solucoes:\n");
    printf("x = %.2f\n", x);
    printf("y = %.2f\n", y);
    printf("z = %.2f\n", z);

    return 0;
}
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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
}