84 lines
1.7 KiB
C
84 lines
1.7 KiB
C
/* Algorithme de Thomas */
|
|
|
|
#include <stdio.h>
|
|
|
|
// Pas testé
|
|
|
|
// 1)
|
|
|
|
double D3diag(int n, double* a, double* b, double* c) {
|
|
double D[n];
|
|
int i;
|
|
D[0] = b[0];
|
|
D[1] = b[0] * b[1] - a[1] * c[0];
|
|
for (i = 2; i < n; i++) {
|
|
D[i] = b[i] * D[i-1] - a[i] * c[i-1] * D[i-2];
|
|
}
|
|
return D[i];
|
|
}
|
|
|
|
// 2)
|
|
|
|
#define N_MAX 100
|
|
|
|
int main() {
|
|
// -
|
|
int n;
|
|
printf("Saisir la dimension n du système : ");
|
|
scanf("%d", &n);
|
|
|
|
if (n < 3 || n > N_MAX) {
|
|
printf("N doit doit être compris entre 3 et %d", N_MAX);
|
|
}
|
|
|
|
// -
|
|
double a[n], b[n], c[n], y[n];
|
|
|
|
int i;
|
|
for (i = 1; i < n; i++) {
|
|
printf("Saisissez l'élément %d de la diagonale A : ", i);
|
|
scanf("%lf", &a[i]);
|
|
}
|
|
for (i = 0; i < n; i++) {
|
|
printf("Saisissez l'élément %d de la diagonale B : ", i);
|
|
scanf("%lf", &b[i]);
|
|
}
|
|
for (i = 0; i < n-1; i++) {
|
|
printf("Saisissez l'élément %d de la diagonale C : ", i);
|
|
scanf("%lf", &c[i]);
|
|
}
|
|
for (i = 0; i < n; i++) {
|
|
printf("Saisissez l'élément %d du second membre y : ", i);
|
|
scanf("%lf", &y[i]);
|
|
}
|
|
|
|
// -
|
|
double G[n], B[n], x[n];
|
|
|
|
G[0] = c[0] / b[0];
|
|
B[0] = y[0] / b[0];
|
|
|
|
for (i = 1; i < n-1; i++) {
|
|
G[i] = c[i] / (b[i] - a[i] * G[i-1]);
|
|
}
|
|
|
|
for (i = 1; i < n; i++) {
|
|
B[i] = (y[i] - a[i] * B[i-1]) / (b[i] - a[i] * G[i-1]);
|
|
}
|
|
|
|
x[n-1] = B[n-1];
|
|
for (i = n-2; i >= 0; i--) {
|
|
x[i] = B[i] - G[i] * x[i+1];
|
|
}
|
|
|
|
// -
|
|
printf("Déterminant de T : %lf\n", D3diag(n, a, b, c));
|
|
|
|
printf("X = ");
|
|
for (i = 1; i < n; i++) {
|
|
printf("%11lf ", x[i]);
|
|
}
|
|
printf("\n");
|
|
|
|
}
|