Sort Matrix by Diagnoal(py & js)

Author: Gaurav-pandey04

.DS_Store

@@ -0,0 +1,119 @@
+{
+ "cells": [
+ {
+ "cell_type": "markdown",
+ "id": "e78585ec",
+ "metadata": {},
+ "source": [
+ "# Sort matrix by diagonal"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": 12,
+ "id": "81aac26f",
+ "metadata": {},
+ "outputs": [],
+ "source": [
+ "from collections import defaultdict\n",
+ "\n",
+ "grid = [[1,7,3],[9,8,2],[4,5,6]]\n",
+ "\n",
+ "n = len(grid)\n",
+ "diagonals = defaultdict(list)"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": 13,
+ "id": "98da3a63",
+ "metadata": {},
+ "outputs": [
+ {
+ "name": "stdout",
+ "output_type": "stream",
+ "text": [
+ "defaultdict(<class 'list'>, {0: [1, 8, 6], -1: [7, 2], -2: [3], 1: [9, 5], 2: [4]})\n"
+ ]
+ }
+ ],
+ "source": [
+ "#Step 1: Collecting the diagonals\n",
+ "for i in range(n):\n",
+ " for j in range(n):\n",
+ " diagonals[i-j].append(grid[i][j])\n",
+ "\n",
+ "print(diagonals)"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": 14,
+ "id": "d6ef687f",
+ "metadata": {},
+ "outputs": [
+ {
+ "name": "stdout",
+ "output_type": "stream",
+ "text": [
+ "defaultdict(<class 'list'>, {0: [8, 6, 1], -1: [2, 7], -2: [3], 1: [9, 5], 2: [4]})\n"
+ ]
+ }
+ ],
+ "source": [
+ "#Step 2: Sort the diagnoals\n",
+ "for key in diagonals:\n",
+ " if key >=0: # Bottom - left triangle\n",
+ " diagonals[key].sort(reverse=True) # Non - increasing order\n",
+ " else: # Top - right triangle\n",
+ " diagonals[key].sort() # Non - decreasing order\n",
+ "\n",
+ "print(diagonals)"
+ ]
+ },
+ {
+ "cell_type": "code",
+ "execution_count": 15,
+ "id": "ca11a32c",
+ "metadata": {},
+ "outputs": [
+ {
+ "name": "stdout",
+ "output_type": "stream",
+ "text": [
+ "[[8, 2, 3], [9, 6, 7], [4, 5, 1]]\n"
+ ]
+ }
+ ],
+ "source": [
+ "#Step 3: Put them Back\n",
+ "for i in range(n):\n",
+ " for j in range(n):\n",
+ " grid[i][j] = diagonals[i-j].pop(0)\n",
+ "\n",
+ "print(grid)"
+ ]
+ }
+ ],
+ "metadata": {
+ "kernelspec": {
+ "display_name": "Python 3",
+ "language": "python",
+ "name": "python3"
+ },
+ "language_info": {
+ "codemirror_mode": {
+ "name": "ipython",
+ "version": 3
+ },
+ "file_extension": ".py",
+ "mimetype": "text/x-python",
+ "name": "python",
+ "nbconvert_exporter": "python",
+ "pygments_lexer": "ipython3",
+ "version": "3.13.3"
+ }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 5
+}

Arrays/.DS_Store

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+// Sort Matrix by Diagnoal 
+
+grid = [[1,7,3],[9,8,2],[4,5,6]];
+
+const n = grid.length;
+const diagonals = {};
+
+// Step 1: collect diagonals
+for(let i=0; i<n; i++){
+ for(let j=0; j<n; j++){
+ const key = i-j;
+ if(!diagonals[key]) diagonals[key] = [];
+ diagonals[key].push(grid[i][j]);
+ }
+}
+
+// Step 2: Sort the diagnoals
+for(const key in diagonals){
+ const k = parseInt(key);
+ if(key >=0 ){
+ diagonals[key].sort((a,b)=>b-a); // non - increasing
+ }else{
+ diagonals[key].sort((a,b)=>a-b); // non - decreasing
+ }
+}
+
+// Step 3: Refil the grid
+for(let i=0; i<n; i++){
+ for(let j =0; j<n; j++){
+ const key = i-j;
+ grid[i][j] = diagonals[key].shift();
+ }
+}
+
+console.log(grid)