Knapsack

{
  "algorithm_version": "knapsack-01-dp-v1",
  "evidence": {
    "dp_capacity": 7,
    "dp_items": 3,
    "optimality_proof": false,
    "transcript_encoding": "dpValue[0..capacity] as signed int64 two's-complement, 8-byte big-endian, no prefix",
    "transcript_sha256": "ec9c54475ee83fff14d13c4bc4728d2d22b27125fcf88ed76782a0425e758ecf",
    "verification": "recompute the bounded dynamic program; the digest detects transcript drift but is not an optimality proof"
  },
  "objective": "maximum_total_value",
  "objective_value": 9,
  "operation": "knapsack",
  "optimal": true,
  "solution": {
    "remaining_capacity": 0,
    "selected": [
      {
        "id": "camera",
        "original_index": 0,
        "value": 4,
        "weight": 3
      },
      {
        "id": "battery",
        "original_index": 1,
        "value": 5,
        "weight": 4
      }
    ],
    "used_capacity": 7
  },
  "warnings": [],
  "work_units": 24
}

# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i -X POST 'https://decision-solver.use.x402atlas.com/knapsack' \
  -H 'content-type: application/json' \
  --data-raw '{"capacity":7,"items":[{"id":"camera","value":4,"weight":3},{"id":"battery","value":5,"weight":4},{"id":"tripod","value":6,"weight":5}]}'

# x402 v2 sends the challenge base64-encoded in the PAYMENT-REQUIRED header (v1 sends it in the body).
# To read the header:
curl -sS -g -o /dev/null -D - -X POST 'https://decision-solver.use.x402atlas.com/knapsack' \
  -H 'content-type: application/json' \
  --data-raw '{"capacity":7,"items":[{"id":"camera","value":4,"weight":3},{"id":"battery","value":5,"weight":4},{"id":"tripod","value":6,"weight":5}]}' \
  | grep -i '^payment-required:' | cut -d' ' -f2 | tr -d '\r' | base64 --decode

// npm i @x402/fetch @x402/evm viem
import { wrapFetchWithPayment, x402Client } from "@x402/fetch";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

// Pays at most $0.005 per call.
const client = new x402Client().setSpendControls({ maxAmountPerPayment: "$0.005" });
registerExactEvmScheme(client, { signer: privateKeyToAccount(process.env.EVM_PRIVATE_KEY) });
const pay = wrapFetchWithPayment(fetch, client);

// Not sure it's safe to pay? ToolVet checks it first for $0.005. Pay for that from a separate
// client: this one is capped at $0.005 per payment. GET https://toolvet.app/api/v1/check?url=https%3A%2F%2Fdecision-solver.use.x402atlas.com%2Fknapsack&method=POST
const res = await pay("https://decision-solver.use.x402atlas.com/knapsack", {
  method: "POST",
  headers: { "content-type": "application/json" },
  body: JSON.stringify({
    "capacity": 7,
    "items": [
      {
        "id": "camera",
        "value": 4,
        "weight": 3
      },
      {
        "id": "battery",
        "value": 5,
        "weight": 4
      },
      {
        "id": "tripod",
        "value": 6,
        "weight": 5
      }
    ]
  }),
});
console.log(res.status, await res.text());

# pip install "x402[requests,evm]"
import os
from eth_account import Account
from x402 import x402ClientSync
from x402.http.clients import x402_requests
from x402.mechanisms.evm import EthAccountSigner
from x402.mechanisms.evm.exact.register import register_exact_evm_client

# Pays at most $0.005 per call.
client = x402ClientSync().set_spend_controls({"max_amount_per_payment": "$0.005"})
register_exact_evm_client(client, EthAccountSigner(Account.from_key(os.environ["EVM_PRIVATE_KEY"])))

with x402_requests(client) as session:
    res = session.post(
        "https://decision-solver.use.x402atlas.com/knapsack",
        json={
            "capacity": 7,
            "items": [
                {
                    "id": "camera",
                    "value": 4,
                    "weight": 3,
                },
                {
                    "id": "battery",
                    "value": 5,
                    "weight": 4,
                },
                {
                    "id": "tripod",
                    "value": 6,
                    "weight": 5,
                },
            ],
        },
    )
    print(res.status_code, res.text)