From 87ce07f3a935460dc2cbccc3f4acec93ce5ffc5c Mon Sep 17 00:00:00 2001
From: ult-sohtome <a.sohtome@ultinet.co.jp>
Date: Mon, 18 Mar 2024 16:12:40 +0900
Subject: [PATCH] adding-up-practice

---
 app.js | 44 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)

diff --git a/app.js b/app.js
index ad9a93a..90c7cb3 100644
--- a/app.js
+++ b/app.js
@@ -1 +1,45 @@
 '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});
+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) {
+    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 pair1[1].change - pair2[1].change;
+  });
+  const rankingStrings = rankingArray.map(([key, value], i) => {
+    return `${i+1}位 ${key}: ${value.before}=>${value.after} 変化率:${value.change}`;
+  });
+  console.log(rankingStrings);
+});
+