From fc6bbb4bd90e86861d96660e90c154d1a6f1ce40 Mon Sep 17 00:00:00 2001
From: Ashton94089 <100675001+Ashton94089@users.noreply.github.com>
Date: Sun, 6 Mar 2022 22:44:31 +0800
Subject: [PATCH] Update 5_practice.c
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

L16104105 陳柏頴
作業練習，離散傅立葉轉換
我發現實部的值怪怪的，暫時不知道如何解決
---
 5_practice.c | 36 ++++++++++++++++++++++++------------
 1 file changed, 24 insertions(+), 12 deletions(-)

diff --git a/5_practice.c b/5_practice.c
index 70d6651..f6ecb00 100644
--- a/5_practice.c
+++ b/5_practice.c
@@ -9,30 +9,42 @@ int main() {
 	time_t t;
 
 	// Input the number N
-	
+	printf("Please input an integer : ");
+	scanf("%d",&N);
 	
 	// Locate the memory for x, yr, yi;
-
-	// Initial setting for x, for example, x[k] = k
-	
-	
+	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;
+	}
 	
 	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++){
+		yr[n] = cos(0)*x[0];
+		yi[n] = (-1)*sin(0)*x[0];
+		for(k=1;k<N;k++){
+			yr[n] = yr[n] + cos(2*M_PI*n*k/N)*x[k];
+			yi[n] = yi[n] - sin(2*M_PI*n*k/N)*x[k];
+		}
+	}
+
+	for(n=0;n<N;n++){
+		printf("n = %d, yr[%d]+i*yi[%d] = %f + i * %f\n",n, n, n, yr[n], yi[n]);
+	}
 
 	// output the results
 	t = clock() - t;
 	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;