Completed stage 1

geometry.c

@@ -17,7 +17,40 @@
 #include "common.h"
 #endif
 
-char *getBisectorEquation(vertex_t *vertexA, vertex_t *vertexB) {
-    printf("x: %lf y: %lf\n", vertexA->x, vertexB->y);
-    return "hi";
+bisector_t getBisector(vertex_t *pointA, vertex_t *pointB) {
+    bisector_t newBisector;
+    double midpointX = (pointA->x + pointB->x) / 2;
+    double midpointY = (pointA->y + pointB->y) / 2;
+
+    newBisector.x = midpointX;
+    newBisector.y = midpointY;
+
+    /* Calculating bisector slope according to slope of AB */
+    if (pointA->x == pointB->x) {
+        /* The line segment AB has an infinite gradient, 
+         * so the orthogonal line will have zero slope.
+         */
+        newBisector.slope = 0;
+        newBisector.isSlopeInfinite = 0;
+    } else if (pointA->y == pointB->y) {
+        /* The line segment AB has gradient of zero, so 
+         * the orthogonal line will have an infinite slope. 
+         */
+        newBisector.isSlopeInfinite = 1;
+
+        /* Not actually zero, just a placeholder to prevent 
+         * accidental errors 
+         */
+        newBisector.slope = 0;
+    } else {
+        /* Slope of the line segment AB */
+        double segmentSlope = \
+            (pointB->y - pointA->y) / (pointB->x - pointA->x);
+
+        /* Calculate orthogonal slope */
+        newBisector.isSlopeInfinite = 0;
+        newBisector.slope = -1 / segmentSlope;
+    }
+
+    return newBisector;
 }

geometry.h

@@ -6,4 +6,14 @@ typedef struct vertex {
     double y;
 } vertex_t;
 
+typedef struct bisector {
+    int isSlopeInfinite;    
+    double slope;
+    double x;
+    double y;
+} bisector_t;
+
+/* Calculates and returns the equation of a bisector of two points */
+bisector_t getBisector(vertex_t *vertexA, vertex_t *vertexB); 
+
 #endif

output.txt

@@ -0,0 +1,6 @@
+y = 0.000000 * (x - 145.600000) + -34.700000
+y = 0.000000 * (x - 145.600000) + -35.200000
+x = 147.100000
+x = 147.100000
+x = 147.600000
+y = 1.000000 * (x - 147.600000) + -33.200000

voronoi.c

@@ -22,15 +22,6 @@
 #define MAX_FIELD_LEN 128
 #define NUM_CSV_FIELDS 6
 
-struct tower {
-    char *id;
-    char *postcode;
-    char *manager;
-    int population;
-    double x;
-    double y;
-};
-
 tower_t **readTowers(tower_t **towers, FILE *datasetFile, int *numTowers) {
     /* Maximum length of a single CSV line */
     size_t lineBufferSize = MAX_CSV_ENTRY_LEN + 1;
@@ -120,7 +111,7 @@ void freeTowers(tower_t **towers, int numTowers) {
 
 vertex_t **readPoints(vertex_t **points, FILE *pointsFile, int *numPoints) {
     /* Current length of a single points line */
-    size_t lineBufferSize = 1;
+    size_t lineBufferSize = 50;
 
     /* Stores the current line from the points file */
     char *lineBuffer = malloc(lineBufferSize * sizeof(*lineBuffer));
@@ -169,10 +160,24 @@ void stage1(char *pointsFileName, char *outputFileName) {
     pointsFile = safeFileOpen(&pointsFile, pointsFileName, "r");
     outputFile = safeFileOpen(&outputFile, outputFileName, "w");
     
-    vertex_t **points = malloc(sizeof(*points));
+    /* Points are given as pairs, so initialise 2 points */
+    vertex_t **points = malloc(sizeof(*points) * 2);
     checkNullPointer(points);
     int numPoints = 0;
-    // points = readPoints(points, pointsFile, &numPoints);
+    points = readPoints(points, pointsFile, &numPoints);
+
+    /* For each pair, calculate and print the bisector to outputFile */
+    for (int i = 0; i < numPoints; i += 2) {
+        bisector_t currBisector = getBisector(points[i], points[i + 1]);
+
+        /* Cannot print infinite slope, so print only x-intercept */
+        if (currBisector.isSlopeInfinite) {
+            fprintf(outputFile, "x = %lf\n", currBisector.x);
+        } else {
+            fprintf(outputFile, "y = %lf * (x - %lf) + %lf\n", \
+                currBisector.slope, currBisector.x,  currBisector.y);
+        }
+    }
 
     freePoints(points, numPoints);
     fclose(pointsFile);

voronoi.h

@@ -5,20 +5,30 @@
 #ifndef VORONOI_HEADER
 #define VORONOI_HEADER
 
-typedef struct tower tower_t;
+typedef struct tower {
+    char *id;
+    char *postcode;
+    char *manager;
+    int population;
+    double x;
+    double y;
+} tower_t;
 
 /* Reads the CSV file and stores the information in the towers array */
 tower_t **readTowers(tower_t **towers, FILE *datasetFile, int *numTowers);
 
-/* Reads the current row from the CSV into a new tower */
+/* Reads the current row from the CSV and converts it into a new tower */
 void readCurrentTower(char *lineBuffer, tower_t *tower);
 
-/* Takes a line from the CSV and converts the data into a tower_t format */
+/* Frees all towers in a towers array */
 void freeTowers(tower_t **towers, int numTowers);
 
 /* Reads a points file and stores the information in the points array */
 vertex_t **readPoints(vertex_t **points, FILE *pointsFile, int *numPoints);
 
+/* Frees all points from a points array */
+void freePoints(vertex_t **points, int numPoints);
+
 /* Outputs the bisector equations from pointsFile into outputFile */
 void stage1(char *pointsFileName, char *outputFileName);