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authorJack Sangdahl <[email protected]>2024-12-21 17:32:46 -0700
committerJack Sangdahl <[email protected]>2024-12-21 17:32:46 -0700
commit27f5c468d6732af671cebc250ad5079e98f2b7e2 (patch)
treef039954848db59f47fe524eaa823bd6619b43bf2 /find_building_alice_bob_meet.cpp
parentc4bf635f931df151edbbbf47be3b37c730d9beed (diff)
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2940. find building where alice and bob can meet
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+// 2940. Find Building Where Alice and Bob Can Meet
+#include "leetcode.h"
+
+/*
+ * you are given a 0-indexed array 'heights' of positive integers where
+ * 'heights[i]' represents the height of the i'th building. if a person is in
+ * building 'i', they can move to any other building 'j' if and only if 'i < j'
+ * and 'heights[i] < heights[j]'. you are also given an array 'queries' where
+ * 'queries[i] = [a_i, b_i]'. on the i'th query, alice is in building 'a_i', and
+ * bob is in building 'b_i'. return array 'ans' where 'ans[i]' is the index of
+ * the leftmost building where alice and bob can meet on i'th query. if alice
+ * and bob cannot move to a common building on query 'i', set 'ans[i]' to -1
+ */
+
+class Solution {
+public:
+ vector<int> leftmostBuildingQueries(vector<int> &heights,
+ vector<vector<int>> &queries) {
+ int hn = heights.size(), qn = queries.size();
+ vector<vector<vector<int>>> q(hn);
+ priority_queue<vector<int>, vector<vector<int>>, greater<vector<int>>> pq;
+ vector<int> ans(qn, -1);
+ for (int qi = 0; qi < qn; qi++) {
+ int i = queries[qi][0], j = queries[qi][1];
+ if (i < j && heights[i] < heights[j])
+ ans[qi] = j;
+ else if (i > j && heights[i] > heights[j])
+ ans[qi] = i;
+ else if (i == j)
+ ans[qi] = i;
+ else
+ q[max(i, j)].push_back({max(heights[i], heights[j]), qi});
+ }
+ for (int i = 0; i < hn; i++) {
+ while (!pq.empty() && pq.top()[0] < heights[i]) {
+ ans[pq.top()[1]] = i;
+ pq.pop();
+ }
+ for (auto &j : q[i])
+ pq.push(j);
+ }
+ return ans;
+ }
+};
+
+int main() {
+ Solution obj;
+ vector<int> h1 = {6, 4, 8, 5, 2, 7}, h2 = {5, 3, 8, 2, 6, 1, 4, 6};
+ vvd(int) q1 = {{0, 1}, {0, 3}, {2, 4}, {3, 4}, {2, 2}},
+ q2 = {{0, 7}, {3, 5}, {5, 2}, {3, 0}, {1, 6}};
+ vector<int> lmbq1 = obj.leftmostBuildingQueries(h1, q1);
+ vector<int> lmbq2 = obj.leftmostBuildingQueries(h2, q2);
+ for (auto i : lmbq1)
+ printf("%d ", i); // expect: 2 5 -1 5 2
+ printf("\n");
+ for (auto i : lmbq2)
+ printf("%d ", i); // expect: 7 6 -1 4 6
+ printf("\n");
+}