leetcode

Daily Problem

3 files changed, 60 insertions(+), 0 deletions(-)

diff --git a/ Problems/1579.cpp b/ Problems/1579.cpp

@@ -0,0 +1,56 @@

class UnionFind {

int n, cnt = n;

vector<int> root, size;

public:

UnionFind(int n) : n(n), root(n), size(n, 1) {

iota(root.begin(), root.end(), 0);

}

UnionFind(const UnionFind &uf)

: n(uf.n), cnt(uf.cnt), root(uf.root), size(uf.size) {}

static int redundant;

int find(int x) {

while (x != root[x]) x = root[x] = root[root[x]];

return x;

}

void join(int x, int y) {

x = find(x), y = find(y);

if (x != y) {

if (size[x] > size[y]) swap(x, y);

root[x] = y;

size[y] += size[x];

cnt--;

} else

redundant++;

}

int count() { return cnt; }

bool connected(int x, int y) { return find(x) == find(y); }

};

int UnionFind::redundant = 0;

class Solution {

public:

int maxNumEdgesToRemove(int n, vector<vector<int>> &e) {

UnionFind::redundant = 0;

UnionFind a(n + 1);

for (int i = 0; i < e.size(); i++)

if (e[i][0] == 3) a.join(e[i][1], e[i][2]);

UnionFind b = a;

for (int i = 0; i < e.size(); i++)

if (e[i][0] == 1)

a.join(e[i][1], e[i][2]);

else if (e[i][0] == 2)

b.join(e[i][1], e[i][2]);

// count must be 2, since 0 is not used

return a.count() == 2 && b.count() == 2 ? UnionFind::redundant : -1;

}

};

diff --git a/ README.md b/ README.md

@@ -455,6 +455,7 @@ for solving problems. | 1544 | Easy | [Make The String Great](Problems/1544.cpp) | | 1557 | Medium | [Minimum Number of Vertices to Reach All Nodes](Problems/1557.cpp) | | 1567 | Medium | [Maximum Length of Subarray With Positive Product](Problems/1567.cpp) |

| 1579 | Hard | [Remove Max Number of Edges to Keep Graph Fully Traversable](Problems/1579.cpp) |

| 1584 | Medium | [Min Cost to Connect All Points](Problems/1584.cpp) | | 1609 | Medium | [Even Odd Tree](Problems/1609.cpp) | | 1615 | Medium | [Maximal Network Rank](Problems/1615.cpp) |

diff --git a/ Templates/Union_Find.cpp b/ Templates/Union_Find.cpp

@@ -7,6 +7,9 @@ public: iota(root.begin(), root.end(), 0); }

UnionFind(const UnionFind &uf)

: n(uf.n), cnt(uf.cnt), root(uf.root), size(uf.size) {}

int find(int x) { while (x != root[x]) x = root[x] = root[root[x]]; return x;