leetcode_pratice/1530/solution.cpp at master · Cuda-Chen/leetcode_pratice · GitHub

Name: leetcode_pratice/1530/solution.cpp at master · Cuda-Chen/leetcode_pratice · GitHub
Rating: 4.9 (3767 reviews)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
/**
 * Definition for a binary tree node.
 * struct TreeNode {
 * int val;
 * TreeNode *left;
 * TreeNode *right;
 * TreeNode() : val(0), left(nullptr), right(nullptr) {}
 * TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 * TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
*/
classSolution {
public:
intcountPairs(TreeNode* root, int distance) {
 unordered_map<TreeNode *, unordered_set<TreeNode *>> g;
 unordered_set<TreeNode *> leaves;
build(root, nullptr, g, leaves);

int ans = 0;
for(auto u : leaves) {
 queue<TreeNode *> q;
 unordered_set<TreeNode *> seen;
int tmp = distance + 1;
 q.push(u);
while(tmp--) {
int sz = q.size();
while(sz--) {
auto t = q.front();
 q.pop();
if(leaves.count(t) && t != u)
 ans++;
if(seen.count(t))
continue;
 seen.insert(t);
for(auto v : g[t])
 q.push(v);
 }
 }
 }
return ans / 2;
 }

private:
voidbuild(
 TreeNode *root,
 TreeNode *p,
 unordered_map<TreeNode *, unordered_set<TreeNode *>> &g,
 unordered_set<TreeNode *> &leaves
 ) {
if(!root)
return;

if(!g.count(root))
 g[root] = {};
if(p) {
 g[p].insert(root);
 g[root].insert(p);
 }
if(!root->left && !root->right) {
 leaves.insert(root);
return;
 }
if(root->left)
build(root->left, root, g, leaves);
if(root->right)
build(root->right, root, g, leaves);
 }

voiddfs(
 unordered_map<TreeNode *, unordered_set<TreeNode *>> &g,
 TreeNode *u,
 TreeNode *v,
 unordered_set<TreeNode *> &seen,
int &ans,
int d
 ) {
if(seen.count(u))
return;
if(d < 0)
return;
if(u == v) {
if(d >= 0)
 ans++;
return;
 }

 seen.insert(u);
 d--;
for(auto w : g[u])
dfs(g, w, v, seen, ans, d);
 }
};