From d8b353ca1b9ec7e5bc4299a9099082bb33c47098 Mon Sep 17 00:00:00 2001
From: Prasham Mehta <133197683+PrashamMehta-04@users.noreply.github.com>
Date: Tue, 7 Oct 2025 21:46:00 +0530
Subject: [PATCH] Add files via upload
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You are given an n x n square matrix of integers grid. Return the matrix such that:
-> The diagonals in the bottom-left triangle (including the middle diagonal) are sorted in non-increasing order.
-> The diagonals in the top-right triangle are sorted in non-decreasing order.

Approach:
We need to sort the diagonals of a square matrix in two different orders depending on their position:

Bottom-left triangle diagonals (including the main diagonal) → non-increasing order
Top-right triangle diagonals → non-decreasing order

The matrix can be divided into diagonals starting from the first column and diagonals starting from the first row (except the main diagonal). For each diagonal, we:
-> Extract all elements
-> Sort them in the required order (ascending for top-right, descending for bottom-left)
-> Place them back into their original positions

Intuition:
A diagonal in an n×n matrix is uniquely determined by its starting position either from the first column (for bottom-left diagonals) or from the first row (for top-right diagonals). By sorting each diagonal individually and placing it back, we can achieve the desired matrix arrangement efficiently.
---
 3446. Sort Matrix by Diagonals.cpp | 70 ++++++++++++++++++++++++++++++
 1 file changed, 70 insertions(+)
 create mode 100644 3446. Sort Matrix by Diagonals.cpp

diff --git a/3446. Sort Matrix by Diagonals.cpp b/3446. Sort Matrix by Diagonals.cpp
new file mode 100644
index 0000000..11ccb7e
--- /dev/null
+++ b/3446. Sort Matrix by Diagonals.cpp	
@@ -0,0 +1,70 @@
+class Solution {
+public:
+    vector<vector<int>> sortMatrix(vector<vector<int>>& grid) {
+        vector<vector<int>> ans;
+        vector<int> t;
+        int cnt = 1;
+        int j=0;
+        for(int i=grid.size()-1;i>=0;i--){
+            int p=i;
+            while(j < grid.size() && p < grid.size()){
+                t.push_back(grid[p][j]);
+                p++;
+                j++;
+            }
+            sort(t.begin(), t.end());
+            reverse(t.begin(), t.end());
+            ans.push_back(t);
+            t.clear();
+            j=0;
+        }
+        vector<vector<int>> a1;
+        int r = 1;
+        for(int k=1;k<grid.size();k++){
+            int q = 0;
+            int d = r;
+            while(q < grid.size() && d < grid.size()){
+                t.push_back(grid[q][d]);
+                q++;
+                d++;
+            }
+            sort(t.begin(), t.end());
+            a1.push_back(t);
+            t.clear();
+            r++;
+        }
+        for(int i=0;i<a1.size();i++){
+            ans.push_back(a1[i]);
+        }
+        j = grid.size()-1;
+        int p = 0,q=0;
+        for(int i=grid.size()-1;i>=0;i--){
+            int r = i;
+            while(q < ans[p].size()){
+                grid[r][j] = ans[p][q];
+                q++;
+                r++;
+                j++;
+            } 
+            j=0;
+            q=0;
+            p++;
+        }
+        q=0;
+        j=1;
+        r=0;
+        for(int i=1;i<grid.size();i++){
+            while(q < ans[p].size()){
+                grid[r][j] = ans[p][q];
+                q++;
+                r++;
+                j++;
+            }
+            j=i+1;
+            r=0;
+            q=0;
+            p++;
+        }
+        return grid;
+    }
+};
\ No newline at end of file