Add solution day 9

day_9/example.txt

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+2333133121414131402

day_9/solve_1.ts

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+export async function readDiskData(path: string) {
+    const text = await Deno.readTextFile(path);
+    return text.trim().split("").map(Number);
+}
+
+export type Block = {
+    id: number;
+} | null;
+
+export function translateToBlocks(data: number[]) {
+    const blocks: Block[] = [];
+    let idGen = 0;
+    let empty = false;
+    for (const num of data) {
+        if (empty) {
+            for (let i = 0; i < num; i++) {
+                blocks.push(null);
+            }
+        } else {
+            const id = idGen++;
+            for (let i = 0; i < num; i++) {
+                blocks.push({ id });
+            }
+        }
+        empty = !empty;
+    }
+    return blocks;
+}
+
+export function compressBlocks(blocks: Block[]) {
+    let left = 0;
+    let right = blocks.length - 1;
+    while (left < right) {
+        // advance left if it's empty
+        if (blocks[left] !== null) {
+            left++;
+            continue;
+        }
+        // advance right if it's not empty
+        if (blocks[right] === null) {
+            right--;
+            continue;
+        }
+        // swap left and right
+        blocks[left] = blocks[right];
+        blocks[right] = null;
+        left++;
+    }
+    return blocks;
+}
+
+export function displayBlocks(blocks: Block[]) {
+    const strs = [];
+    for (const block of blocks) {
+        if (block === null) {
+            strs.push(".");
+        } else {
+            strs.push(block.id);
+        }
+    }
+    console.log(strs.join(""));
+}
+
+if (import.meta.main) {
+    const data = await readDiskData("input.txt");
+    const blocks = translateToBlocks(data);
+    // displayBlocks(blocks);
+    compressBlocks(blocks);
+    // displayBlocks(blocks);
+
+    // multiply index and sum
+    const result = blocks.reduce((acc, block, i) => {
+       if (block === null) {
+        return acc;
+        }
+        return acc + block.id * i;
+    }, 0);
+    console.log(result);
+}
+    

day_9/solve_2.ts

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+import { Block, displayBlocks, readDiskData, translateToBlocks } from "./solve_1.ts";
+
+function newCompressBlocks(blocks: Block[]) {
+    
+    function findEmptySpace(size: number, limit = blocks.length) {
+        // find empty spaces
+        let start = -1;
+        for (let i = 0; i < limit; i++) {
+            if (blocks[i] === null) {
+                if (start === -1) {
+                    start = i;
+                }
+            } else {
+                if (start !== -1) {
+                    if (i - start >= size) {
+                        return start;
+                    }
+                    start = -1;
+                }
+            }
+        }
+        return -1;
+    }
+
+    // compress blocks
+    let right = blocks.length - 1;
+    while (right > 0) {
+        if (blocks[right] === null) {
+            right--;
+            continue;
+        }
+        // get the size of the block
+        let size = 1;
+        let id = blocks[right]!.id;
+        for (let i = right - 1; i >= 0; i--) {
+            if (blocks[i] === null || blocks[i]!.id !== id) {
+                break;
+            }
+            size++;
+        }
+        // find empty space
+        const start = findEmptySpace(size, right);
+        // console.log("Moved block", start, size, id);
+        if (start === -1) {
+            // no empty space found
+            right = right - size;
+            continue;
+        }
+        // move block
+        for (let i = 0; i < size; i++) {
+            blocks[start + i] = blocks[right - i];
+            blocks[right - i] = null;
+        }
+        right = right - size;
+    }
+    return blocks;
+}
+
+if (import.meta.main) {
+    const data = await readDiskData("input.txt");
+    const blocks = translateToBlocks(data);
+    displayBlocks(blocks);
+    newCompressBlocks(blocks);
+    displayBlocks(blocks);
+
+    // multiply index and sum
+    const result = blocks.reduce((acc, block, i) => {
+       if (block === null) {
+        return acc;
+        }
+        return acc + block.id * i;
+    }, 0);
+    console.log(result);
+}