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1572-Matrix_Diagonal_Sum.cpp
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1572-Matrix_Diagonal_Sum.cpp
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/*******************************************************************************
* 1572-Matrix_Diagonal_Sum.cpp
* Billy.Ljm
* 08 May 2023
*
* =======
* Problem
* =======
* https://leetcode.com/problems/matrix-diagonal-sum/
*
* Given a square matrix mat, return the sum of the matrix diagonals.
*
* Only include the sum of all the elements on the primary diagonal and all the
* elements on the secondary diagonal that are not part of the primary diagonal.
*
* ===========
* My Approach
* ===========
* The only way is to iterate through each diagonal element and sum them up.
*
* This has a time complexity of O(n) and space complexity of O(1), where n is
* width of the square matrix
******************************************************************************/
#include <iostream>
#include <vector>
/**
* Solution
*/
class Solution {
public:
/**
* Sums the diagonal elements of a square matrix
*
* @param mat matrix to sum
*
* @return sum of the diagonal elements
*/
int diagonalSum(std::vector<std::vector<int>>& mat) {
int summ = 0; // sum of diagonal elements
size_t w = mat.size() - 1; // width of matrix
// sum diagonal elements
for (int i = 0; i < mat.size(); i++) {
summ = summ + mat[i][i];
if (w - i != i) {
summ = summ + mat[i][w - i];
}
}
return summ;
}
};
/**
* << operator for vectors
*/
template <typename T>
std::ostream& operator<<(std::ostream& os, const std::vector<T>& v) {
os << "[";
for (int i = 0; i < v.size(); i++) {
os << v[i] << ",";
}
os << "\b]";
return os;
}
/**
* Test cases
*/
int main(void) {
Solution sol;
std::vector<std::vector<int>> mat;
// test case 1
mat = { {1, 2, 3}, {4, 5, 6}, {7, 8, 9} };
std::cout << "diagonalSum(" << mat << ") = " << sol.diagonalSum(mat) << std::endl;
// test case 2
mat = { {1, 1, 1, 1}, {1, 1, 1, 1}, {1, 1, 1, 1}, {1, 1, 1, 1} };
std::cout << "diagonalSum(" << mat << ") = " << sol.diagonalSum(mat) << std::endl;
// test case 3
mat = { {5} };
std::cout << "diagonalSum(" << mat << ") = " << sol.diagonalSum(mat) << std::endl;
return 0;
}