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fix code - major errors + add docs

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Krishna Vedala 2020-07-01 21:27:12 -04:00
parent 5daeb8daaa
commit ccd3f66608
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GPG Key ID: BA19ACF8FC8792F7
1 changed files with 34 additions and 11 deletions
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45
searching/modified_binary_search.c
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@ -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;
}