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65 lines
1.5 KiB
Zig
65 lines
1.5 KiB
Zig
const std = @import("std");
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pub fn main() !void {
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// const times = [_]u8{ 7, 15, 30 };
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// const distances = [_]u8{ 9, 40, 200 };
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const times = [_]u8{ 50, 74, 86, 85 };
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const distances = [_]u16{ 242, 1017, 1691, 1252 };
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// Part 1
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var totals: u64 = 1;
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for (times, 0..) |time, idx| {
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var waysToWin: u8 = 0;
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for (0..time) |ms| {
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var dist: u16 = 0;
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for (0..time - ms) |_| {
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dist += @intCast(ms);
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}
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if (dist > distances[idx]) {
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waysToWin += 1;
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}
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}
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totals *= waysToWin;
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}
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std.debug.print("Part 1: {d}\n", .{totals});
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// Part 2
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// const time = 71530;
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// const distance = 940200;
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const time = 50748685;
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const distance = 242101716911252;
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var pivot: u32 = time / 2;
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var max: u32 = pivot;
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var min: u32 = 0;
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var prev: u32 = pivot;
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var i: u8 = 0;
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while (true) : (i += 1) {
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var dist: u64 = 0;
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for (0..(time - pivot)) |_| {
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dist += pivot;
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}
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if (dist > distance) {
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max = pivot;
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pivot -= (max - min) / 2;
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} else {
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min = pivot;
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pivot += (max - min) / 2;
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}
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if (prev == pivot) {
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break;
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}
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prev = pivot;
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}
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const num = time - (pivot * 2);
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std.debug.print("Part 2: {}\n", .{num});
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// TODO: potentially off by one. Could actually figure it out or just try num + 1 in AoC
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}
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