From f14a7b4cb7547b62a039bb1a2ebcb648c5326f5a Mon Sep 17 00:00:00 2001
From: isokaze <isokaze7@gmail.com>
Date: Tue, 28 Jul 2026 22:03:34 +0900
Subject: [PATCH 1/2] =?UTF-8?q?=E3=83=95=E3=82=A1=E3=82=A4=E3=83=AB?=
 =?UTF-8?q?=E3=81=AE=E6=9B=B8=E3=81=8D=E5=87=BA=E3=81=97=E3=82=92=E8=BF=BD?=
 =?UTF-8?q?=E5=8A=A0?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 app.js | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/app.js b/app.js
index ad9a93a..9f37030 100644
--- a/app.js
+++ b/app.js
@@ -1 +1,17 @@
 'use strict';
+const fs = require('node:fs');
+const readline = require('node:readline');
+const rs = fs.createReadStream('./popu-pref.csv');
+const rl = readline.createInterface({ input: rs });
+rl.on('line', lineString => {
+  const columns = lineString.split(',');
+  const year = parseInt(columns[0]);
+  const prefecture = columns[1];
+  const popu = parseInt(columns[3]);
+  if (year === 2016 || year === 2021){
+    console.log(year);
+    console.log(prefecture);
+    console.log(popu);
+  }
+
+});
\ No newline at end of file

From 8df4466c326a76de6dc6caa36629aeff4652da98 Mon Sep 17 00:00:00 2001
From: isokaze <isokaze7@gmail.com>
Date: Mon, 3 Aug 2026 10:38:58 +0900
Subject: [PATCH 2/2] =?UTF-8?q?=E3=83=A9=E3=83=B3=E3=82=AD=E3=83=B3?=
 =?UTF-8?q?=E3=82=B0=E3=81=AE=E5=AE=9F=E8=A3=85=E5=AE=8C=E4=BA=86?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 app.js | 33 ++++++++++++++++++++++++++++++---
 1 file changed, 30 insertions(+), 3 deletions(-)

diff --git a/app.js b/app.js
index 9f37030..e6598ea 100644
--- a/app.js
+++ b/app.js
@@ -3,15 +3,42 @@ const fs = require('node:fs');
 const readline = require('node:readline');
 const rs = fs.createReadStream('./popu-pref.csv');
 const rl = readline.createInterface({ input: rs });
+const prefectureDataMap = new Map(); // key: 都道府県 value: 集計データのオブジェクト
 rl.on('line', lineString => {
   const columns = lineString.split(',');
   const year = parseInt(columns[0]);
   const prefecture = columns[1];
   const popu = parseInt(columns[3]);
   if (year === 2016 || year === 2021){
-    console.log(year);
-    console.log(prefecture);
-    console.log(popu);
+    let value = null;
+    if (prefectureDataMap.has(prefecture)) {
+      value = prefectureDataMap.get(prefecture);
+    } else {
+      value = {
+        before: 0,
+        after: 0,
+        change: null
+      };
+    }
+    if (year === 2016) {
+      value.before = popu;
+    }
+    if (year === 2021) {
+      value.after = popu;
+    }
+    prefectureDataMap.set(prefecture, value);
   }
 
+});
+rl.on('close', () => {
+  for (const [key, value] of prefectureDataMap){
+    value.change = value.after / value.before;
+  }
+  const rankingArray = Array.from(prefectureDataMap).sort((pair1, pair2) => {
+    return pair2[1].change - pair1[1].change;
+  });
+  const rankingStrings = rankingArray.map(([key, value]) => {
+    return `${key}: ${value.before}=>${value.after} 変化率: ${value.change}`;
+  });
+  console.log(rankingStrings);
 });
\ No newline at end of file