Check if a line at 45 degree can divide the plane into two equal weight parts in C++

Suppose we have n different points (Xi, Yi) in 2D coordinate and each point has a weight Wi, we have to check whether a line at 45 degree can be drawn. So that the sum of weights of points on each side will be same.

So, if the input is like[[-1,1,3],[-2,1,1],[1,-1,4]], then the output will be True/

To solve this, we will follow these steps −

n := size of v
Define one map weight_at_x
max_x := -2000, min_x := 2000
for initialize i := 0, when i < n, update (increase i by 1), do −
- temp_x := v[0, i] - v[1, i]
- max_x := maximum of max_x and temp_x
- min_x := minimum of min_x and temp_x
- weight_at_x[temp_x] := weight_at_x[temp_x] + v[2, i]
Define an array sum_temp
insert 0 at the end of sum_temp
for initialize x := min_x, when x <= max_x, update (increase x by 1), do −
- insert (last element of sum_temp + weight_at_x[x]) at the end of sum_temp
total_sum := last element of sum_temp
partition_possible := false
for initialize i := 1, when i < size of sum_temp, update (increase i by 1), do −
- if sum_temp[i] is same as total_sum - sum_temp[i], then −
  - partition_possible := true
- if sum_temp[i - 1] is same as total_sum - sum_temp[i], then −
  - partition_possible := true
return partition_possible

Example

Let us see the following implementation to get better understanding −

Live Demo

#include <bits/stdc++.h>
using namespace std;
void is_valid_part(vector<vector<int>> &v){
   int n = v.size();
   map<int, int> weight_at_x;
   int max_x = -2000, min_x = 2000;
   for (int i = 0; i < n; i++) {
      int temp_x = v[0][i] - v[1][i];
      max_x = max(max_x, temp_x);
      min_x = min(min_x, temp_x);
      weight_at_x[temp_x] += v[2][i];
   }
   vector<int> sum_temp;
   sum_temp.push_back(0);
   for (int x = min_x; x <= max_x; x++) {
      sum_temp.push_back(sum_temp.back() + weight_at_x[x]);
   }
   int total_sum = sum_temp.back();
   int partition_possible = false;
   for (int i = 1; i < sum_temp.size(); i++) {
      if (sum_temp[i] == total_sum - sum_temp[i])
         partition_possible = true;
      if (sum_temp[i - 1] == total_sum - sum_temp[i])
         partition_possible = true;
   }
   printf(partition_possible ? "TRUE" : "FALSE");
}
int main() {
   vector<vector<int>> v = {{-1,1,3},{-2,1,1},{1,-1,4}};
   is_valid_part(v);
}