day 23: #24, #687. for part 2 I considered the solution a few times ("I should use a linked list so inserts will be faster") but missed the critical step of having a value_map so finding is instant too. and then I fumbled around with the linked list for a while. I had it mostly done but not quite because I was missing the final set to end = current and that took a while to find

Author: pfgithub

2020/solutions/day23/d23.zig

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+const std = @import("std");
+
+pub fn range(max: usize) []const void {
+    return @as([]const void, &[_]void{}).ptr[0..max];
+}
+
+pub fn main() !void {
+    var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
+    defer arena.deinit();
+    const alloc = &arena.allocator;
+    const array_space = try alloc.alloc(usize, 20_000_000);
+    
+    var array: []usize = array_space[0..1_000_000];
+    
+    for(range(1_000_000)) |_, i| {
+        array[i] = i + 1;
+    }
+    for("389125467") |char, i| {
+        array[i] = (char - '0');
+    }
+    
+    for(range(10_000_000)) |_, iter_index| {
+        const current = array[0];
+        const three = array[1..4];
+        array = array[4..];
+        array.len += 4;
+        // this is going to be too slow isn't it
+        var searchv = current - 1;
+        if(searchv == 0) searchv = array.len;
+        for(range(3)) |_| {
+            for(three) |v| {
+                if(searchv == v) searchv -= 1;
+                if(searchv == 0) searchv = array.len;
+            }
+        }
+        const foundi = for(array) |v, i| {
+            if(v == searchv) break i;
+        } else std.debug.panic("Did not find {} in array", .{searchv});
+        // 2 1 0 3
+        // 2 . . . 1 0 3
+        // TODO if it's faster, go the other direction?
+        std.mem.copyBackwards(usize, array[foundi + 4..], array[foundi + 1..array.len - 3]);
+        std.mem.copy(usize, array[foundi + 1..foundi + 4], three);
+        array[array.len - 1] = current;
+    
+        if(iter_index % 1_000 == 0) std.log.emerg("iter index: {}", .{iter_index});
+    }
+}

2020/solutions/day23/day23.1.ts

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+/*
+input: string, lines: string[], dblines: string[][]
+copy(text: string) → clipboard
+error(message: string) → thrown error
+-5..mod(3) → @mod(-5, 3)
+*/
+
+// Cardinals:
+// [[1,0],[-1,0],[0,1],[0,-1]]
+// +Diagonals:
+// [[1,0],[-1,0],[0,1],[0,-1],[-1,-1],[-1,1],[1,-1],[1,1]]
+
+export {};
+
+let cups = input.split("").map(v => +v);
+
+const move = () => {
+	let current = cups.shift();
+	let [a, b, c] = [cups.shift(), cups.shift(), cups.shift()];
+	let findv = current;
+	let foundi: number;
+	while(true) {
+		findv -= 1;
+		findv = findv.mod(10);
+		foundi = cups.findIndex((q) => q == findv);
+		if(foundi == -1) continue;
+		break;
+	}
+	[a, b, c].forEach((v, i) => {
+		cups.splice(foundi + i + 1, 0, v);
+	})
+	cups.push(current);
+	print(cups.join(", "));
+}
+
+for(let i = 0; i < 100; i++) move();
+
+print(cups.join(","));
+
+while(cups[0] !== 1) {
+	cups.push(cups.shift());
+}
+cups.shift();
+
+print(cups.join(""));

2020/solutions/day23/day23.2.ts

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+/*
+input: string, lines: string[], dblines: string[][]
+copy(text: string) → clipboard
+error(message: string) → thrown error
+-5..mod(3) → @mod(-5, 3)
+*/
+
+// Cardinals:
+// [[1,0],[-1,0],[0,1],[0,-1]]
+// +Diagonals:
+// [[1,0],[-1,0],[0,1],[0,-1],[-1,-1],[-1,1],[1,-1],[1,1]]
+
+export {};
+
+// 389125467
+// 28915467 … 3
+// 5467 … 891 3 2
+// … 891 3 467 2 5
+
+let cups = "389125467".split("").map(v => +v);
+
+let starti = cups.length + 1;
+print(starti);
+while(cups.length < 1000000) {
+	cups.push(starti);
+	starti += 1;
+}
+
+// 10,000,000 times:
+// take four from the start
+// find the number either 1-, 2-, 3-, or 4- the first one taken, depending on the next three
+// insert the three after that
+// insert the first at the end
+// very fast
+
+// so 
+
+print(cups);
+error("bye");
+
+const move = () => {
+	let current = cups.shift();
+	let [a, b, c] = [cups.shift(), cups.shift(), cups.shift()];
+	let findv = current;
+	let foundi: number;
+	while(true) {
+		findv -= 1;
+		findv = findv.mod(10);
+		foundi = cups.findIndex((q) => q == findv);
+		if(foundi == -1) continue;
+		break;
+	}
+	[a, b, c].forEach((v, i) => {
+		cups.splice(foundi + i + 1, 0, v);
+	})
+	cups.push(current);
+	// print(cups.join(", "));
+}
+
+for(let i = 0; i < 10000000; i++) move();
+
+print(cups.join(","));
+
+while(cups[0] !== 1) {
+	cups.push(cups.shift());
+}
+cups.shift();
+
+print(cups.shift(), cups.shift());

2020/solutions/day23/day23.3.ts

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+/*
+input: string, lines: string[], dblines: string[][]
+copy(text: string) → clipboard
+error(message: string) → thrown error
+-5..mod(3) → @mod(-5, 3)
+*/
+
+// Cardinals:
+// [[1,0],[-1,0],[0,1],[0,-1]]
+// +Diagonals:
+// [[1,0],[-1,0],[0,1],[0,-1],[-1,-1],[-1,1],[1,-1],[1,1]]
+
+
+type thisv = [number, thisv]
+let cups: thisv[] = input.split("").map(v => [+v]) as any as thisv[];
+
+let starti = cups.length + 1;
+print(starti);
+while(cups.length < 1000000) {
+	cups.push([starti] as any as thisv);
+	starti += 1;
+}
+
+let start = cups[0];
+
+cups.forEach((v, i) => {
+    v[1] = cups[(i + 1) % cups.length];
+});
+
+let end = cups[cups.length - 1];
+
+const value_map: thisv[] = [];
+
+cups.forEach(q => {
+    value_map[q[0]] = q;
+});
+
+// ok no one cares about the cups array anymore
+
+const move = () => {
+	
+    let current = start;
+    start = start[1];
+
+    let a = start;
+    start = start[1];
+    let b = start;
+    start = start[1];
+    let c = start;
+    start = start[1];
+
+    end[1] = start;
+
+	let findv = current[0] - 1;
+    if(findv == 0) findv = cups.length;
+    if(findv == a[0] || findv == b[0] || findv == c[0]) findv -= 1;
+    if(findv == 0) findv = cups.length;
+    if(findv == a[0] || findv == b[0] || findv == c[0]) findv -= 1;
+    if(findv == 0) findv = cups.length;
+    if(findv == a[0] || findv == b[0] || findv == c[0]) findv -= 1;
+    if(findv == 0) findv = cups.length;
+
+    let found = value_map[findv];
+
+    if(found == end) end = c;
+    c[1] = found[1];
+    found[1] = a;
+
+    end[1] = current;
+    current[1] = start;
+	end = current;
+}
+
+for(let i = 0; i < 10000000; i++) {
+    move();
+}
+
+const oneloc = value_map[1];
+
+print(oneloc[1][0] * oneloc[1][1][0]);
+

2020/solutions/day23/day23.4.ts

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+/*
+input: string, lines: string[], dblines: string[][]
+copy(text: string) → clipboard
+error(message: string) → thrown error
+-5..mod(3) → @mod(-5, 3)
+*/
+
+// Cardinals:
+// [[1,0],[-1,0],[0,1],[0,-1]]
+// +Diagonals:
+// [[1,0],[-1,0],[0,1],[0,-1],[-1,-1],[-1,1],[1,-1],[1,1]]
+
+export {};
+

2020/solutions/day23/day23.5.ts

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+/*
+input: string, lines: string[], dblines: string[][]
+copy(text: string) → clipboard
+error(message: string) → thrown error
+-5..mod(3) → @mod(-5, 3)
+*/
+
+// Cardinals:
+// [[1,0],[-1,0],[0,1],[0,-1]]
+// +Diagonals:
+// [[1,0],[-1,0],[0,1],[0,-1],[-1,-1],[-1,1],[1,-1],[1,1]]
+
+export {};
+

2020/solutions/day23/day23.txt

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+362981754