L16101123 Hw3

5_practice.c

@@ -9,31 +9,60 @@ int main() {
 	time_t t;
 
 	// Input the number N
-
+	printf("Please input a number N\n");
+	scanf("%d",&N);
 
 	// Locate the memory for x, yr, yi;
-
+    x  = (double *)malloc(N * sizeof(double));
+	yr = (double *)malloc(N * sizeof(double)); 
+	yi = (double *)malloc(N * sizeof(double));  
 	// Initial setting for x, for example, x[k] = k
 
-
-
+	for (k=0;k<N;k++){
+		x[k] = k;
+		yr[k] = 0;
+		yi[k] = 0;
+	}
 
 	t = clock();	
 	// yr[n]+i*yi[n] = sum(exp(-i 2 Pi k n / N)*x[k], k=0..N-1), n=0..N-1 
 
-
-
-
-
+	for ( n = 0; n < N; n++){
+		for ( k = 0; k < N; k++){
+			yr[n] += cos(2 * M_PI * k * n / N ) * x[k];
+			yi[n] -= sin(2 * M_PI * k * n / N ) * x[k];
+		}
+	}
 
 
 	// output the results
 	t = clock() - t;
+	printf("Result \n");
+	printf("x = (");
+	for (k = 0; k < N; k++)
+	{
+		if (k % 10 == 0 && k > 1)
+			printf("\n  ");
+		printf(" %.0f ", x[k]);
+	}
+	printf(" )\n");
+
+	printf("F(x) = \n");
+	printf("( ");
+	for (n = 0; n < N; n++)
+	{
+		if (n % 5 == 0 && n > 1)
+			printf("\n  ");
+		printf(" %.2f %+.2fi ", yr[n], yi[n]);
+	}
+	printf(" )\n");
+
 	printf("%d ms for discrete Fourier Transform of %d elements\n", t, N);
 
 	// free the memory located by x, yr, yi
-
-
+	free(x);
+	free(yr);
+	free(yi);
 
 	return 100;
 }