exercism/zig/knapsack/knapsack.zig

const std = @import("std");
const mem = std.mem;

pub const Item = struct {
    weight: usize,
    value: usize,

    pub fn init(weight: usize, value: usize) Item {
        return Item{ .weight = weight, .value = value };
    }
};

pub fn maximumValue(allocator: mem.Allocator, maximumWeight: usize, items: []const Item) !usize {
    if (items.len == 0) return 0;

    var dp: []usize = try allocator.alloc(usize, maximumWeight + 1);
    defer allocator.free(dp);
    @memset(dp, 0);

    for (items) |item| {
        var maxW = maximumWeight;
        while (maxW > 0) : (maxW -= 1) {
            if (item.weight <= maxW) {
                dp[maxW] = @max(dp[maxW], dp[maxW - item.weight] + item.value);
            }
        }
    }

    return dp[maximumWeight];
}