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distances.c
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distances.c
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/**
* Copyright (c) 2020 Robert M. Vunabandi
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include "./distances.h"
#include "./alphabet.h"
#include <assert.h>
#include <stdbool.h>
#include <stdlib.h>
//
// First, defining functions to be used by the API functions in distance.h
//
/**
* A data structure to hold two characters in sorted order using the
* ALPHABET defined in `alphabet.h` for ordering.
*
* Invariants:
* - Both `first` and `second` appear in the ALPHABET
* - `first` appears before or in the same place as `second` in the ALPHABET
* - `second` appears after or in the same place as `first` in the ALPHABET
*/
typedef struct SortedChar {
char first;
char second;
} SortedChar;
/**
* This method is very self explanatory.
*
* Precondition:
* - s1 and s2 are in ALPHABET (i.e., lowercase alphanumeric)
*/
SortedChar getSortedChar(char s1, char s2) {
// Time Complexity: ALPHABET_LENGTH
char first = '\0';
char second = '\0';
#ifdef DEBUG
bool broke = false;
#endif
for (int i = 0; i < ALPHABET_LENGTH; i++) {
if (s1 == ALPHABET[i]) {
first = s1;
second = s2;
#ifdef DEBUG
broke = true;
#endif
break;
}
if (s2 == ALPHABET[i]) {
first = s2;
second = s1;
#ifdef DEBUG
broke = true;
#endif
break;
}
}
#ifdef DEBUG
assert(broke);
#endif
return (SortedChar) {.first = first, .second = second};
}
/**
* This computes the number of letters it takes to go from `first` to `second`
* in the alphabet. In case second appears before first in the alphabet, it
* will wrap around and compute the distance from `first` to "z" + 1 + distance
* from "a" to `second`. Each character counts as 1.
*/
int relativeCharDistance(char first, char second) {
// Time Complexity: WRAPPED_ALPHABET_LENGTH
int firstIdx = -1;
int secondIdx = -1;
for (int i = 0; i < WRAPPED_ALPHABET_LENGTH; i++) {
if (firstIdx == -1) {
assert(secondIdx == -1);
if (first == ALPHABET[i]) {
firstIdx = i;
if (second == ALPHABET[i]) {
secondIdx = i;
break;
}
}
continue;
}
assert(secondIdx == -1);
if (second == ALPHABET[i]) {
secondIdx = i;
break;
}
}
assert(firstIdx != -1);
assert(secondIdx != -1);
int result = secondIdx - firstIdx;
assert(result >= 0);
return result;
}
//
// Definitions for the API in distance.h
//
int hammingDistance(char *s1, char *s2, int m) {
// Time Complexity: m
int result = 0;
for (int i = 0; i < m; i++) {
if (s1[i] != s2[i]) {
result += 1;
}
}
return result;
}
int relativeDistance(char *s1, char *s2, int m) {
// Time Complexity: m * (getSortedChar + relativeCharDIstance)
int result = 0;
for (int i = 0; i < m; i++) {
SortedChar sc = getSortedChar(s1[i], s2[i]);
result += relativeCharDistance(sc.first, sc.second);
}
return result;
}
int rotRelativeDistance(char *s1, char *s2, int m) {
// Time Complexity: 2 * m * relativeCharDistance
int result = 0;
for (int i = 0; i < m; i++) {
int foward = relativeCharDistance(s1[i], s2[i]);
int backward = relativeCharDistance(s2[i], s1[i]);
result += foward < backward ? foward : backward;
}
return result;
}
int pairwiseHammingDistance(char *s1, char *s2, int m) {
int result = 0;
for (int i = 0; i < m; i++) {
for (int j = 0; j < m; j++) {
if (s1[i] != s2[j]) {
result += abs(j - i) + 1;
}
}
}
return result;
}