2a

two.js

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+const { readFile } = require('fs/promises');
+
+// 2a
+async function init() {
+  const input = await readFile('two.txt', 'utf8');
+  // const input = await readFile('two.test.txt', 'utf8');
+  const data = input.split('\n');
+
+  let score = 0;
+
+  data.forEach((d) => {
+    const [opp, me] = d.split(' ');
+
+    score += play(opp, me);
+    score += value(me);
+  });
+
+  console.log(score);
+}
+
+function play(opp, me) {
+  if (me === 'X') {
+    if (opp === 'A') {
+      return 3;
+    }
+    if (opp === 'B') {
+      return 0;
+    }
+    if (opp === 'C') {
+      return 6;
+    }
+  }
+  if (me === 'Y') {
+    if (opp === 'A') {
+      return 6;
+    }
+    if (opp === 'B') {
+      return 3;
+    }
+    if (opp === 'C') {
+      return 0;
+    }
+  }
+  if (me === 'Z') {
+    if (opp === 'A') {
+      return 0;
+    }
+    if (opp === 'B') {
+      return 6;
+    }
+    if (opp === 'C') {
+      return 3;
+    }
+  }
+}
+
+function value(me) {
+  if (me === 'X') {
+    return 1;
+  }
+  if (me === 'Y') {
+    return 2;
+  }
+  if (me === 'Z') {
+    return 3;
+  }
+
+  throw new Error('bad me', me);
+}
+
+init();

two.test.txt

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+A Y
+B X
+C Z