Weekly Contest 307

Author: MaskRay

amount-of-time-for-binary-tree-to-be-infected.cc

@@ -0,0 +1,25 @@
+// Amount of Time for Binary Tree to Be Infected
+class Solution {
+  int start, ans = 0;
+  pair<int, int> dfs(TreeNode *x) {
+    int h = 0, dep = x->val == start ? 0 : -1;
+    for (auto *y : {x->left, x->right}) {
+      if (!y) continue;
+      auto [h1, dep1] = dfs(y);
+      if (dep >= 0)
+        ans = max(ans, dep+1+h1);
+      else if (dep1 >= 0) {
+        ans = max(ans, h+1+dep1);
+        dep = dep1+1;
+      }
+      h = max(h, h1+1);
+    }
+    return {h, dep};
+  }
+public:
+  int amountOfTime(TreeNode* root, int start) {
+    this->start = start;
+    dfs(root);
+    return ans;
+  }
+};

find-the-k-sum-of-an-array.cc

@@ -0,0 +1,25 @@
+// Find the K-Sum of an Array
+class Solution {
+public:
+  long long kSum(vector<int>& a, int k) {
+    long n = a.size(), sum = 0;
+    for (int &x : a)
+      if (x < 0)
+        x = -x;
+      else
+        sum += x;
+    sort(a.begin(), a.end());
+    priority_queue<pair<long, int>> pq;
+    pq.emplace(sum-a[0], 0);
+    while (--k) {
+      auto [s, i] = pq.top();
+      sum = s;
+      pq.pop();
+      if (i+1 < n) {
+        pq.emplace(s+a[i]-a[i+1], i+1);
+        pq.emplace(s-a[i+1], i+1);
+      }
+    }
+    return sum;
+  }
+};

largest-palindromic-number.cc

@@ -0,0 +1,28 @@
+// Largest Palindromic Number
+#define REP(i, n) for (long i = 0; i < (n); i++)
+#define ROF(i, a, b) for (long i = (b); --i >= (a); )
+
+class Solution {
+public:
+  string largestPalindromic(string num) {
+    int c[10] = {};
+    string ret;
+    for (char x : num)
+      c[x-'0']++;
+    ROF(i, 0, 10) {
+      if (i == 0 && ret.empty())
+        continue;
+      ret.insert(ret.end(), c[i]/2, '0'+i);
+      c[i] %= 2;
+    }
+    int n = ret.size();
+    ROF(i, 0, 10)
+      if (c[i]) {
+        ret.push_back('0'+i);
+        break;
+      }
+    REP(i, n)
+      ret += ret[n-1-i];
+    return ret;
+  }
+};

minimum-hours-of-training-to-win-a-competition.cc

@@ -0,0 +1,18 @@
+// Minimum Hours of Training to Win a Competition
+#define REP(i, n) for (long i = 0; i < (n); i++)
+
+class Solution {
+public:
+  int minNumberOfHours(int a, int b, vector<int>& en, vector<int>& ex) {
+    int n = en.size(), s = 0;
+    REP(i, n) {
+      if (a <= en[i])
+        s += en[i]+1-a, a = en[i]+1;
+      if (b <= ex[i])
+        s += ex[i]+1-b, b = ex[i]+1;
+      a -= en[i];
+      b += ex[i];
+    }
+    return s;
+  }
+};