http://adventofcode.com/2017/day/2 - Solidity - Demo: https://remix.ethereum.org/#version=soljson-v0.4.20-nightly.2017.12.4+commit.240c79e6.js

aoc2017-Day2.sol.js

contract Day2 {
    uint constant SPACE    = 32;
    uint constant NEW_LINE = 10;
    
    bytes public b;
    uint[] public stack;

    function Day2() public {
        string memory puzzle = "5 1 9 5\n7 5 3\n2 4 6 8";
        b = bytes(puzzle);
    }

    function getAnswer() public view returns (uint answer) {
        answer = 0;
        uint min = 0;
        uint max = 0;
        
        for (uint i = 0; i < b.length; i++) {
            uint v = uint(b[i]);
            
            if (v == SPACE) { continue; }
            
            if (v == NEW_LINE) {
                answer += (max - min);
                min = 0;
                max = 0;
                continue;
            }
            
            v -= 48;
            
            if (min == 0 || v <= min) { min = v; }
            if (max == 0 || v >= max) { max = v; }
        }
        
        return answer + (max - min);
    }
}