From bab919b5f225efdf9b7926928eab7584d566a458 Mon Sep 17 00:00:00 2001
From: Tamaki Naito <tnaito.0367@gmail.com>
Date: Sat, 11 Feb 2023 11:21:34 +0900
Subject: [PATCH] =?UTF-8?q?=E4=BA=BA=E5=8F=A3=E6=B8=9B=E5=B0=91=E7=8E=87?=
 =?UTF-8?q?=E3=81=AE=E3=83=A9=E3=83=B3=E3=82=AD=E3=83=B3=E3=82=B0=E4=BD=9C?=
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---
 app.js | 42 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/app.js b/app.js
index ad9a93a..ccb61fc 100644
--- a/app.js
+++ b/app.js
@@ -1 +1,43 @@
 'use strict';
+const fs = require("fs");
+const readline = require("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 === 2010 || year === 2015){
+    let value = null;
+    if(prefectureDataMap.has(prefecture)){
+        value = prefectureDataMap.get(prefecture);
+    }else{
+        value = {
+            popu10: 0,
+            popu15: 0,
+            change: null
+        };
+    }
+    if(year === 2010){
+        value.popu10 = popu;
+    }
+    if(year === 2015){
+        value.popu15 = popu;
+    }
+    prefectureDataMap.set(prefecture, value);
+   } 
+});
+rl.on("close", ()=>{
+    for(const[prefecture, value] of prefectureDataMap){
+        value.change = value.popu15 / value.popu10;
+    }
+    const rankingArray = Array.from(prefectureDataMap).sort((pair1, pair2) =>{
+        return pair1[1].change - pair2[1].change;
+    });
+    const rankingStrings = rankingArray.map(([prefecture, value], i) =>{
+        return `第${i + 1}位: ${prefecture}: ${value.popu10} => ${value.popu15} change: ${value.change}`;
+    })
+    console.log(rankingStrings);
+});
\ No newline at end of file