fix code - major errors + add docs

searching/modified_binary_search.c

@@ -1,10 +1,21 @@
+/**
+ * @file
+ * @brief [Modified binary search algorithm](https://arxiv.org/abs/1406.1677)
+ */
 #include <stdio.h>
 #include <stdlib.h>
 
-int n, m;  // size of the matrix
-
-// This function does Binary search for x in i-th row from j_low to j_high.
-void binarySearch(int **mat, int i, int j_low, int j_high, int x)
+/** This function does Binary search for `x` in `i`-th row from `j_low` to
+ * `j_high`.
+ * @param mat 2D matrix to search within
+ * @param i row to search in
+ * @param j_low start column index
+ * @param j_high end column index
+ * @param x value to search for
+ * @return column where `x` was found
+ * @return -1 if value not found
+ */
+int binarySearch(const int **mat, int i, int j_low, int j_high, int x)
 {
     while (j_low <= j_high)
     {
@@ -14,20 +25,27 @@ void binarySearch(int **mat, int i, int j_low, int j_high, int x)
         if (mat[i][j_mid] == x)
         {
             printf("Found at (%d,%d)\n", i, j_mid);
-            return;
+            return j_mid;
         }
         else if (mat[i][j_mid] > x)
             j_high = j_mid - 1;
         else
             j_low = j_mid + 1;
     }
+
     // element not found
     printf("element not found\n");
+    return -1;
 }
 
-// Function to perform binary search on the mid values of row to get the desired
-// pair of rows where the element can be found
-void modifiedBinarySearch(int **mat, int n, int m, int x)
+/** Function to perform binary search on the mid values of row to get the
+ * desired pair of rows where the element can be found
+ * @param [in] mat matrix to search for the value in
+ * @param n number of rows in the matrix
+ * @param m number of columns in the matrix
+ * @param x value to search for
+ */
+void modifiedBinarySearch(const int **mat, int n, int m, int x)
 {  // If Single row matrix
     if (n == 1)
     {
@@ -75,12 +93,16 @@ void modifiedBinarySearch(int **mat, int n, int m, int x)
         binarySearch(mat, i_low + 1, j_mid + 1, m - 1, x);
 }
 
+/** Main function */
 int main()
 {
-    int x;  // element to be searched
+    int x;     // element to be searched
+    int m, n;  // m = columns, n = rows
+
     scanf("%d %d %d\n", &n, &m, &x);
+
     int **mat = (int **)malloc(n * sizeof(int *));
-    for (x = 0; x < n; x++) mat[x] = (int *)malloc(m * sizeof(int));
+    for (int i = 0; i < m; i++) mat[i] = (int *)malloc(m * sizeof(int));
 
     for (int i = 0; i < n; i++)
     {
@@ -89,9 +111,10 @@ int main()
             scanf("%d", &mat[i][j]);
         }
     }
+
     modifiedBinarySearch(mat, n, m, x);
 
-    for (x = 0; x < n; x++) free(mat[x]);
+    for (int i = 0; i < n; i++) free(mat[i]);
     free(mat);
     return 0;
 }