62 lines
1.8 KiB
Zig
62 lines
1.8 KiB
Zig
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const std = @import("std");
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pub fn main() void {
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const input = @embedFile("input");
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var iter = std.mem.split(u8, input, "\n");
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var totalPoints: usize = 0;
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while (iter.next()) |round| {
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// Not a valid round. Not necessary, but just in case
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if (round.len < 3) continue;
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if (round[0] < 'A' or round[0] > 'C') continue;
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if (round[2] < 'X' or round[2] > 'Z') continue;
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// Convert letters to numbers
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const them = round[0] - 'A';
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const result = round[2] - 'X';
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// Now the points per result is easy
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// {0,1,2} * 3 == {0,3,6}
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// which is what we want.
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const resultPoints = result * 3;
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// Now this is a bit more complex.
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// We need some kind of operation that
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// returns us this:
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//
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// them (0,1,2)
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// die(0) {2,0,1} {3,1,2}
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// tie(1) {0,1,2} -+1-> {1,2,3}
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// win(2) {1,2,0} {2,3,1}
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//
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// ex.: if they do rock (0)
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// and I die (0)
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// I have to choose scissors (2)
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// which gives me 3 points (2+1)
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//
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// We notice that 'them + result' gives:
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//
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// them (0,1,2)
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// die(0) {0,1,2}
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// tie(1) {1,2,3}
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// win(2) {2,3,4}
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//
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// If we wrap the results with '(them + result)%3'
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// and then shift it by adding before wrapping
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// '(them + result + 2)%3':
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//
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// them (0,1,2)
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// die(0) {0,1,2} {2,0,1}
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// tie(1) {1,2,0} -+2-> {0,1,2}
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// win(2) {2,0,1} {1,2,0}
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//
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// Now it's just a matter of adding one to that
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const shapePoints = ((them + result + 2) % 3) + 1;
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totalPoints += resultPoints + shapePoints;
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}
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std.debug.print("{}\n", .{totalPoints});
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}
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