Friday, July 22, 2016
C++ Solution to UVA 459 - Graph Connectivity Solution Union by Rank and Path Compression
July 22, 2016
algorithm explanation
,
algorithm to cpp implementation
,
c++
,
commented code
,
disjoint set count
,
graph connectivity solution
,
made easy
,
path compression
,
union by rank
,
uva 459
Problem Link:
https://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&problem=400These are my old codes I kept for visual explanations but I lost all the data. Since these are old codes I can not remember if I made any breaking changes to the code later. For the algorithm please see Introduction to Algorithms book.
Problem Explanation & Visalization:
TODOInput & Output Explanation:
TODOInput & Output:
Input:1 E AB CE DB EC
Output:2
More input and output in udebug:
https://www.udebug.com/UVa/459Code:
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| /** | |
| * Author: Asif Ahmed | |
| * Site: https://quickgrid.wordpress.com | |
| * Problem: UVA 10583 - Ubiquitous Religions | |
| * Technique: Disjoint-Set Forest Union by Rank | |
| * and Path Compression using Structure. | |
| */ | |
| #include<stdio.h> | |
| #include<string.h> | |
| #define N 202 | |
| static char s[2]; | |
| static int parentArray[N]; | |
| static int rankArray[N]; | |
| int disjointSetCount; | |
| // Basically create n sets with elements from | |
| // 0 to n - 1. Reset their rank to 0 since the | |
| // sets have only one element. So each set is | |
| // basically pointing to itself in the parent | |
| // array. | |
| void MakeSet(int n){ | |
| for(int i = 0; i < n; ++i){ | |
| parentArray[i] = i; | |
| rankArray[i] = 0; | |
| } | |
| disjointSetCount = n; | |
| } | |
| // Find the parent of the node and | |
| // do path compression in the process. | |
| int FindSet(int x){ | |
| if( x != parentArray[x] ) | |
| parentArray[x] = FindSet( parentArray[x] ); | |
| return parentArray[x]; | |
| } | |
| // Check if both elements are in the same set. | |
| bool SameSet(int x, int y){ | |
| return FindSet(x) == FindSet(y); | |
| } | |
| // Check if they are already in the same set. | |
| // If not then the tree or Set with the bigger | |
| // rank becomes the parent of tree with smaller | |
| // rank. | |
| // If both have same rank then arbitrarily choose | |
| // one to be the parent of the other set. Here y | |
| // is chosen. | |
| void Link(int x, int y){ | |
| if( !SameSet(x, y) ){ | |
| if( rankArray[x] > rankArray[y] ) | |
| parentArray[y] = x; | |
| else{ | |
| parentArray[x] = y; | |
| if(rankArray[x] == rankArray[y]) | |
| rankArray[y] = rankArray[y] + 1; | |
| } | |
| --disjointSetCount; | |
| } | |
| } | |
| // Union two sets. | |
| // First find their representative and link them. | |
| void Union(int x, int y){ | |
| Link( FindSet(x), FindSet(y) ); | |
| } | |
| int main(){ | |
| //freopen("input.txt", "r", stdin); | |
| //freopen("output.txt", "w", stdout); | |
| int n; | |
| int i, j; | |
| scanf("%d\n\n", &n); | |
| bool blank = false; | |
| while( n-- ){ | |
| char c = getchar(); | |
| getchar(); | |
| MakeSet( c - 'A' + 1); | |
| while( gets(s) && strlen(s) ) | |
| Union( s[0] - 'A' , s[1] - 'A' ); | |
| if(blank) | |
| putchar('\n'); | |
| blank = true; | |
| printf("%d\n", disjointSetCount); | |
| } | |
| return 0; | |
| } |
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