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feat: add union find algorithm (aka disjoint set)

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This commit is contained in:
Leo Yang
2020-01-24 23:22:08 -06:00
parent c168638060
commit 1c5b12323a
1 changed files with 44 additions and 49 deletions
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93
data_structure/disjoint_set.cpp
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@@ -1,69 +1,64 @@
#include <iostream>
#include <vector>
using namespace std;
using std::cout;
using std::endl;
using std::vector;
vector<int> root, rnk;
void CreateSet(int n){
root = vector<int> (n+1);
rnk = vector<int> (n+1, 1);
for(int i = 1; i <= n; ++ i) {
root[i] = i;
}
void CreateSet(int n) {
root = vector<int> (n+1);
rnk = vector<int> (n+1, 1);
for (int i = 1; i <= n; ++i) {
root[i] = i;
}
}
int Find(int x) {
if (root[x] == x) {
return x;
}
return root[x] = Find(root[x]);
if (root[x] == x) {
return x;
}
return root[x] = Find(root[x]);
}
bool InSameUnion(int x, int y) {
return Find(x) == Find(y);
return Find(x) == Find(y);
}
void Union(int x, int y) {
int a = Find(x), b = Find(y);
if(a != b) {
if (rnk[a] < rnk[b]) {
root[a] = b;
} else if (rnk[a] > rnk[b]) {
root[b] = a;
} else {
root[a] = b;
++ rnk[b];
}
int a = Find(x), b = Find(y);
if (a != b) {
if (rnk[a] < rnk[b]) {
root[a] = b;
} else if (rnk[a] > rnk[b]) {
root[b] = a;
} else {
root[a] = b;
++rnk[b];
}
}
}
int main() {
// tests CreateSet & Find
int n = 100;
CreateSet(n);
for (int i = 1; i <= 100; ++ i) {
if (root[i] != i) {
cout << "Fail" << endl;
break;
}
// tests CreateSet & Find
int n = 100;
CreateSet(n);
for (int i = 1; i <= 100; ++i) {
if (root[i] != i) {
cout << "Fail" << endl;
break;
}
// tests InSameUnion & Union
cout << "1 and 2 are initially not in the same subset" << endl;
if (InSameUnion(1, 2)) {
cout << "Fail" << endl;
}
Union(1, 2);
cout << "1 and 2 are now in the same subset" << endl;
if (!InSameUnion(1, 2)) {
cout << "Fail" << endl;
}
return 0;
}
// tests InSameUnion & Union
cout << "1 and 2 are initially not in the same subset" << endl;
if (InSameUnion(1, 2)) {
cout << "Fail" << endl;
}
Union(1, 2);
cout << "1 and 2 are now in the same subset" << endl;
if (!InSameUnion(1, 2)) {
cout << "Fail" << endl;
}
return 0;
}