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Diagonal Traverse in C++
Suppose we have a matrix of M x N elements, we have to find all elements of the matrix in diagonal order. So if the matrix is like −
1 | 2 | 3 |
4 | 5 | 6 |
7 | 8 | 9 |
The output will be [1,2,4,7,5,3,6,8,9]
To solve this, we will follow these steps −
- Make an array ret, set row := 0 and col := 0, n := row count, m := col count, down := false
- for i in range 0 to n – 1
- x := i, y := 0
- create an array temp
- while x >= 0 and y < m, do
- insert matrix[x,y] into temp, and decrease x by 1 and increase y by 1
- if down is true, then reverse the temp array
- for i in range 0 to size of temp – 1, insert temp[i] into ret
- down := inverse of down
- for i in range 1 to m – 1
- x := n – 1, y := 1, create an array temp
- while x >= 0 and y < m,
- insert matrix[x, y] into temp and decrease x by 1 and increase y by 1
- for i in range 0 to size of temp – 1, insert temp[i] into ret
- down := inverse of down
- return ret.
Let us see the following implementation to get better understanding −
Example
#include <bits/stdc++.h> using namespace std; void print_vector(vector<int> v){ cout << "["; for(int i = 0; i<v.size(); i++){ cout << v[i] << ", "; } cout << "]"<<endl; } class Solution { public: vector<int> findDiagonalOrder(vector<vector<int>>& matrix) { vector <int> ret; int row = 0; int col = 0; int n = matrix.size(); int m = n? matrix[0].size() : 0; bool down = false; for(int i = 0; i < n; i++){ int x = i; int y = 0; vector <int> temp; while(x >= 0 && y < m){ temp.push_back(matrix[x][y]); x--; y++; } if(down) reverse(temp.begin(), temp.end()); for(int i = 0; i < temp.size(); i++)ret.push_back(temp[i]); down = !down; } for(int i = 1; i < m; i++){ int x = n - 1; int y = i; vector <int> temp; while(x >= 0 && y < m){ temp.push_back(matrix[x][y]); x--; y++; } if(down) reverse(temp.begin(), temp.end()); for(int i = 0; i < temp.size(); i++)ret.push_back(temp[i]); down = !down; } return ret; } }; main(){ vector<vector<int>> v = {{1,2,3},{4,5,6},{7,8,9}}; Solution ob; print_vector(ob.findDiagonalOrder(v)); }
Input
[[1,2,3],[4,5,6],[7,8,9]]
Output
[1, 2, 4, 7, 5, 3, 6, 8, 9, ]
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