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Queue Reconstruction by Height in C++
Consider we have a random list of people standing in a queue. If each person is described by a pair of integers (h, k), where h is the height and k is the number of people in front of him, who have a height greater than or equal to h. We have to define one method to reconstruct the queue. So if the given array is like [[7,0], [4,4], [7,1], [5,0], [6,1], [5,2]], then the output will be [[5,0], [7,0], [5,2], [6,1], [4,4], [7,1]]
To solve this, we will follow these steps −
- sort the given array based on the following comparison strategy
- if a[0] = b[0], then return a[1] > b[1], otherwise return a[0] < b[0]
- create one vector called ans
- for i in range size of given array down to 0
- insert (first element of ans + p[i, 1], p[i]) into ans array
- return ans
Example
Let us see the following implementation to get a better understanding −
#include <bits/stdc++.h> using namespace std; void print_vector(vector<vector<auto> > v){ cout << "["; for(int i = 0; i<v.size(); i++){ cout << "["; for(int j = 0; j <v[i].size(); j++){ cout << v[i][j] << ", "; } cout << "],"; } cout << "]"<<endl; } bool cmp(vector <int> a, vector <int> b){ if(a[0] == b[0])return a[1] > b[1]; return a[0] < b[0]; } class Solution { public: vector<vector<int>> reconstructQueue(vector<vector<int>>& p) { sort(p.begin(), p.end(), cmp); vector < vector <int> > ans; for(int i = p.size()-1; i>=0; i--){ ans.insert(ans.begin() + p[i][1], p[i]); } return ans; } }; main(){ Solution ob; vector<vector<int>> v = {{7,0}, {4,4}, {7,1}, {5,0}, {6,1}, {5,2}}; print_vector(ob.reconstructQueue(v)); }
Input
[[7,0], [4,4], [7,1], [5,0], [6,1], [5,2]]
Output
[[5,0], [7,0], [5,2], [6,1], [4,4], [7,1]]
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