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Richard SmithandGeoff Romer
ce50f181f1
When a `var` is not explicitly given an initializer, initialize it in one of two ways: * If its type implements the new interface `Core.Default`, call `Core.Default.Op` to initialize it. * Otherwise, if its type implements `UnformedInit`, leave it in an unformed state. For now, this is always an uninitialized state, but that will change in the future. * If neither of those apply, the `var` declaration is ill-formed. This is a step towards implementing leads decision #6739 and proposals #257 and #5913. Assisted-by: Gemini 3.1 Pro via Antigravity --------- Co-authored-by: Geoff Romer <gromer@google.com>
61 lines
1.5 KiB
Plaintext
61 lines
1.5 KiB
Plaintext
// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
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// Exceptions. See /LICENSE for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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// https://adventofcode.com/2024/day/7
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library "day7_common";
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import Core library "io";
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import library "io_utils";
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fn Concat(a_val: i64, b_val: i64) -> i64 {
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var a: i64 = a_val;
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var b: i64 = b_val;
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if (b == 0) {
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return a * 10;
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}
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while (b != 0) {
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a *= 10;
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b /= 10;
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}
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return a + b_val;
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}
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class Equation {
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impl as Core.UnformedInit {}
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fn Read() -> Equation {
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returned var me: Equation;
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me.num_operands = 0;
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ReadInt(ref me.result);
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ConsumeChar(':');
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while (ConsumeChar(' ')) {
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ReadInt(ref me.operands[me.num_operands]);
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++me.num_operands;
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}
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while (SkipNewline()) {}
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return var;
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}
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fn SolveFrom[self: Self](start: i32, value: i64, concat: bool) -> bool {
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if (value > self.result) {
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return false;
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}
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if (start == self.num_operands) {
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return value == self.result;
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}
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return self.SolveFrom(start + 1, value + self.operands[start], concat) or
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self.SolveFrom(start + 1, value * self.operands[start], concat) or
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(concat and self.SolveFrom(start + 1, Concat(value, self.operands[start]), true));
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}
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fn Solve[self: Self](concat: bool) -> bool {
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return self.SolveFrom(1, self.operands[0], concat);
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}
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var operands: array(i64, 16);
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var num_operands: i32;
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var result: i64;
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}
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