Merge pull request #565 from kvedala/lgtm-fixes

[LGTM alerts] fixes to some of the LGTM alerts

misc/cartesian_to_polar.c

@@ -1,50 +1,66 @@
+/**
+ * @file
+ * @brief Function to convert a Cartesian co-ordinate to polar form.
+ */
+#define _USE_MATH_DEFINES /**< required for MS Visual C */
+#include <assert.h>
 #include <math.h>
 #include <stdio.h>
-
-const double pi = 3.141592653589793238462643383279502884;
+#include <stdlib.h>
 
 /**
-give as arguments to the executable two x and y coordinates
-outputs a polar coordinate
-*/
-int main()
+ * @brief Function to convert cartesian coordinates to polar.
+ *\f{eqnarray*}{
+ r &=& \sqrt{x^2+y^2}\\
+ \theta &=& \atan\frac{y}{x}
+ \f}
+ * @param [in] x absicca value
+ * @param [in] y ordinate value
+ * @param [out] r pointer to store polar radius
+ * @param [out] theta pointer to store polar angle (in radian)
+ */
+void to_polar(double x, double y, double *r, double *theta)
 {
-    double x, y;
-    double r, theta, thetaFinal;
-    scanf("%lf %lf", &x, &y);
-    r = hypot(x, y);
+    double thetaFinal = 0.f;
+
+    *r = sqrt(x * x + y * y);
+
     if (x != 0)
     {
         if (y != 0)
         {
-            theta = atan(y / x);
+            *theta = atan(y / x);
             if ((x > 0 && y > 0) || (x == -y))
             {  // Q1
-                thetaFinal = theta;
+                thetaFinal = *theta;
             }
             else if (x < 0 && y > 0)
             {  // Q2
-                thetaFinal = theta + pi;
+                thetaFinal = *theta + M_PI;
             }
             else if (x < 0 && y < 0)
             {  // Q3
-                thetaFinal = theta - pi;
+                thetaFinal = *theta - M_PI;
             }
             else if (x > 0 && y < 0)
             {  // Q4
-                thetaFinal = 2 * pi - theta;
+                thetaFinal = 2 * M_PI - *theta;
+            }
+            else
+            {
+                fprintf(stderr, "Should not reach here!\n");
             }
         }
     }
-    if (x == 0)
+    else
     {  // exceptions when no actual angle is present
         if (y > 0)
         {
-            thetaFinal = pi / 2;
+            thetaFinal = M_PI / 2;
         }
         else
         {
-            thetaFinal = -(pi / 2);
+            thetaFinal = -(M_PI / 2);
         }
     }
     if (y == 0)
@@ -55,8 +71,53 @@ int main()
         }
         else
         {
-            thetaFinal = -pi;
+            thetaFinal = -M_PI;
         }
     }
-    printf("%.2f %.2f\n", r, atan2(y, x));
+
+    *theta = thetaFinal;
+}
+
+/**
+ * @brief Generate a random number in the given limits
+ *
+ * @param lim1 lower limit
+ * @param lim2 upper limit
+ * @return random number in the given range
+ */
+double get_rand(double lim1, double lim2)
+{
+    double r = (double)rand() / RAND_MAX;  // value in [0,1)
+    return (lim2 - lim1) * r + lim1;       // scale to range
+}
+
+/**
+ * @brief Test implementation
+ *
+ */
+void test()
+{
+    srand(10);
+    int NUM_TESTS = 5;
+
+    for (int i = 0; i < NUM_TESTS; i++)
+    {
+        double r, theta;
+        printf("Test %d.... ", i);
+        double x = get_rand(-5, 5);
+        double y = get_rand(-5, 5);
+        printf("(%.2g, %.2g).... ", x, y);
+        to_polar(x, y, &r, &theta);
+        assert(fabs(r - hypot(x, y)) < 0.01);
+        assert(fabs(theta - atan2(y, x)) < 0.01);
+        printf("passed\n");
+    }
+}
+
+/** Main function */
+int main()
+{
+    test();
+
+    return 0;
 }

misc/union_find.c

@@ -1,46 +1,89 @@
+/**
+ * @file union_find.c
+ * @brief [Union
+ * find](https://en.wikipedia.org/wiki/Disjoint-set_data_structure) algorithm.
+ */
 #include <stdio.h>
+#include <stdlib.h>
+#define MAX_SIZE 1000 /**< maximum number of elements in the set */
 
-int p[1000000];
-int find(int x)
+/**
+ * @brief Find index of or value in an array
+ *
+ * @param [in,out] p array to search and update
+ * @param x value to search
+ * @return value at the index `x`
+ */
+int find(int *p, int x)
 {
+    if (x >= MAX_SIZE)
+    {
+        fprintf(stderr, "Out-of bounds value\n");
+        exit(EXIT_FAILURE);
+    }
+
     if (p[x] == x)
     {
         return x;
     }
     else
     {
-        p[x] = find(p[x]);
+        p[x] = find(p, p[x]);
         return p[x];
     }
 }
-// Call to function join(int x, int y) to join PARAM x and y
-void join(int x, int y) { p[find(x)] = find(y); }
 
+/**
+ * @brief Function to join
+ * @param [in,out] p array to join in
+ * @param x value or index to join to
+ * @param y value or index to join from
+ */
+void join(int *p, int x, int y) { p[find(p, x)] = find(p, y); }
+
+/** Main function */
 int main()
 {
-    // Have all array indexes that you need to use refrence themselves
+    int union_set[MAX_SIZE];
+
+    // Have all array indexes that you need to use reference themselves
     for (int i = 0; i < 10; i++)
     {
-        p[i] = i;
+        union_set[i] = i;
     }
     // p = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}
-    join(3, 5);
+
+    join(union_set, 3, 5);
+    printf("The array is now: ");
+    for (int i = 0; i < 10; i++)
+    {
+        printf("%d ", union_set[i]);
+    }
+    printf("\n");
     // Now 3 and 5 are groupped together, that is find(3) = find(5)
     // p = {0, 1, 2, 5, 4, 5, 6, 7, 8, 9}
-    join(3, 8);
+
+    join(union_set, 3, 8);
+    printf("The array is now: ");
+    for (int i = 0; i < 10; i++)
+    {
+        printf("%d ", union_set[i]);
+    }
+    printf("\n");
+
     // Now 3, 5 and are groupped together, find(3) = find(5) = find(8)
     // p = {0, 1, 2, 5, 4, 8, 6, 7, 8, 9}
-    join(0, 5);
-    if (find(0) == find(3))
+    join(union_set, 0, 5);
+    if (find(union_set, 0) == find(union_set, 3))
     {
         printf("0 and 3 are groupped together\n");
     }
     printf("The array is now: ");
     for (int i = 0; i < 10; i++)
     {
-        printf("%d ", p[i]);
+        printf("%d ", union_set[i]);
     }
     printf("\n");
 
     return 0;
-}
+}

searching/jump_search.c

@@ -1,37 +1,85 @@
+/**
+ * @file jump_search.c
+ * @brief Implementation of [jump
+ * search](https://en.wikipedia.org/wiki/Jump_search) algorithm.
+ */
+#include <assert.h>
 #include <math.h>
 #include <stdio.h>
+
+/**
+ * @brief Macro to return the minimum of two values
+ */
 #define min(X, Y) ((X) < (Y) ? (X) : (Y))
-int jump_search(int *arr, int x);
-int n;
 
-int main()
-{
-    int arr[] = {0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610};
-    n = sizeof(arr) / sizeof(int);
-    int x = 55;
-    int index = jump_search(arr, x);
-    printf("\nNumber %d is at index %d\n", x, index);
-}
-
-int jump_search(int *arr, int x)
+/**
+ * @brief Implement Jump-search algorithm
+ *
+ * @param [in] arr Array to search within
+ * @param x value to search for
+ * @param n length of array
+ * @return index where the value was found
+ * @return -1 if value not found
+ */
+int jump_search(const int *arr, int x, size_t n)
 {
     int step = floor(sqrt(n));
     int prev = 0;
-    while (*(arr + (min(step, n) - 1)) < x)
+
+    while (arr[min(step, n) - 1] < x)
     {
         prev = step;
         step += floor(sqrt(n));
         if (prev >= n)
+        {
             return -1;
+        }
     }
 
-    while (*(arr + prev) < x)
+    while (arr[prev] < x)
     {
         prev = prev + 1;
-        if (prev == fmin(step, n))
+        if (prev == min(step, n))
+        {
             return -1;
+        }
     }
-    if (*(arr + prev) == x)
+    if (arr[prev] == x)
+    {
         return prev;
+    }
     return -1;
 }
+
+/**
+ * @brief Test implementation of the function
+ *
+ */
+void test()
+{
+    int arr[] = {0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610};
+    size_t n = sizeof(arr) / sizeof(int);
+
+    int x = 55;
+    printf("Test 1.... ");
+    int index = jump_search(arr, x, n);
+    assert(index == 10);
+    printf("passed\nTest 2.... ");
+    x = 56;
+    index = jump_search(arr, x, n);
+    assert(index == -1);
+    printf("passed\nTest 3.... ");
+    x = 13;
+    index = jump_search(arr, x, n);
+    assert(index == 7);
+    printf("passed\n");
+}
+
+/**
+ * @brief Main function
+ */
+int main()
+{
+    test();
+    return 0;
+}