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Best Meeting Point in C++
Suppose there is a group of two or more people and they wants to meet and minimize the total travel distance. We have a 2D grid of values 0 or 1, where each 1 mark the home of someone in the group. The distance is calculated using the formula of Manhattan Distance, so distance(p1, p2) = |p2.x - p1.x| + |p2.y - p1.y|.
So, if the input is like
| 1 | 0 | 0 | 0 | 1 |
| 0 | 0 | 0 | 0 | 0 |
| 0 | 0 | 1 | 0 | 0 |
then the output will be 6 as from the matrix we can understand that three people living at (0,0), (0,4), and (2,2): The point (0,2) is an ideal meeting point, as the total travel distance of 2+2+2=6 is minimum.
To solve this, we will follow these steps −
Define a function get(), this will take an array v,
sort the array v
i := 0
j := size of v
ret := 0
while i < j, do −
ret := ret + v[j] - v[i]
(increase i by 1)
(decrease j by 1)
return ret
From the main method do the following −
Define an array row
Define an array col
for initialize i := 0, when i < size of grid, update (increase i by 1), do −
for initialize j := 0, when j < size of grid[0], update (increase j by 1), do −
if grid[i, j] is non-zero, then −
insert i at the end of row
insert j at the end of col
return get(row) + get(col)
Example
Let us see the following implementation to get better understanding −
#include <bits/stdc++.h>
using namespace std;
class Solution {
public:
int minTotalDistance(vector<vector<int>>& grid) {
vector<int> row;
vector<int> col;
for (int i = 0; i < grid.size(); i++) {
for (int j = 0; j < grid[0].size(); j++) {
if (grid[i][j]) {
row.push_back(i);
col.push_back(j);
}
}
}
return get(row) + get(col);
}
int get(vector <int> v){
sort(v.begin(), v.end());
int i = 0;
int j = v.size() - 1;
int ret = 0;
while (i < j) {
ret += v[j] - v[i];
i++;
j--;
}
return ret;
}
};
main(){
Solution ob;
vector<vector<int>> v = {{1,0,0,0,1},{0,0,0,0,0},{0,0,1,0,0}};
cout << (ob.minTotalDistance(v));
}Input
{{1,0,0,0,1},{0,0,0,0,0},{0,0,1,0,0}}Output
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