How to map char values to int using enum

Question

I am trying to map some chars in a string to some integer values using enum. Please tell where am I going wrong?

enum moves{U,R,D,L};
class Solution {
public:
    bool judgeCircle(string moves) {   

// moves is a string having values like ULLDDRR, ULRD, UULLDDRR 
        int X[] = {0,1,0,-1};
        int Y[] = {1,0,-1,0};

// while iterating the string if I get a 'U' , I want to use it as an index 
//with  U representing the 0th index, R as index=1 and so on.. as specified 
 //in the enum

        int x=0 , y=0;
        enum moves ind;
        for( int i = 0 ; i < moves.length() ; i++ ) {
            ind = moves[i];  // but this line here gives error
            x += X[ind];
            y += Y[ind];
        }

        if(!x && !y)
            return true;
        else
            return false;
    }
};

What exactly are you trying to do? Could you post the full code? — Gabriel
– Gabriel, Commented Jun 1, 2019 at 4:56
Do not define enum if you want to use it as array. If you want to use as enum and still want to access as array here is answer: stackoverflow.com/questions/321801/enum-c-get-by-index — Atul
– Atul, Commented Jun 1, 2019 at 5:02
What you are trying to do cannot be done, and is sort of weird enough that I can't recommend a better option because I don't know why you were trying to do it this way in the first place. — Weak to Enuma Elish
– Weak to Enuma Elish, Commented Jun 1, 2019 at 5:10
To map character values to ints use a std::map<char,int> X = {{'u',0},{'r',1},{'d',0},{'l',-1}}; analogous for Y. — πάντα ῥεῖ
– πάντα ῥεῖ, Commented Jun 1, 2019 at 5:14
...and also you have defined 'moves' twice. First as enum and then as string — Atul
– Atul, Commented Jun 1, 2019 at 5:22

Scheff's Cat · Accepted Answer · 2019-06-01 05:47:32Z

2

I would drop the idea with an enum because I feel it has no use for the actual problem – to map characters to navigation moves. For this, I would use a std::map or a std::unordered_map. (Considering, that there are 4 entries only, the performance difference is probably hard to measure.)

While I was preparing a sample code, πάντα ῥεῖ gave a similar hint. Though, I would even recommend to bundle x and y of moves together:

#include <map>
#include <iomanip>
#include <iostream>

// bundle x and y for a move (which needs both of them)
struct Move {
  int dx, dy;
};

// a type to map chars to moves
using MoveMap = std::map<char, Move>;

// a pre-defined move map
static const MoveMap mapMoves = {
    { 'U', { 0, 1 } },
    { 'R', { 1, 0 } },
    { 'D', { 0, -1 } },
    { 'L', { -1, 0 } }
};

/* a function to use move map
 *
 * id ... one of U R D L
 * x, y ... coordinates (update)
 * return: true if successful, (false e.g. for wrong id)
 */
bool move(char id, int &x, int &y)
{
  const MoveMap::const_iterator iter = mapMoves.find(id);
  return iter != mapMoves.end()
    ? x += iter->second.dx, y += iter->second.dy, true
    : false;
}

// check it out:

int main()
{
  int x = 0, y = 0;
  const char test[] = "ULLDDRR, ULRD, UULLDDRR";
  for (char id : test) {
    std::cout << "(" << x << ", " << y << "): "
      << "Move '" << id << "' -> ";
    if (move(id, x, y)) {
      std::cout << "(" << x << ", " << y << ")\n";
    } else std::cout << "failed\n";
  }
  return 0;
}

Output:

(0, 0): Move 'U' -> (0, 1)
(0, 1): Move 'L' -> (-1, 1)
(-1, 1): Move 'L' -> (-2, 1)
(-2, 1): Move 'D' -> (-2, 0)
(-2, 0): Move 'D' -> (-2, -1)
(-2, -1): Move 'R' -> (-1, -1)
(-1, -1): Move 'R' -> (0, -1)
(0, -1): Move ',' -> failed
(0, -1): Move ' ' -> failed
(0, -1): Move 'U' -> (0, 0)
(0, 0): Move 'L' -> (-1, 0)
(-1, 0): Move 'R' -> (0, 0)
(0, 0): Move 'D' -> (0, -1)
(0, -1): Move ',' -> failed
(0, -1): Move ' ' -> failed
(0, -1): Move 'U' -> (0, 0)
(0, 0): Move 'U' -> (0, 1)
(0, 1): Move 'L' -> (-1, 1)
(-1, 1): Move 'L' -> (-2, 1)
(-2, 1): Move 'D' -> (-2, 0)
(-2, 0): Move 'D' -> (-2, -1)
(-2, -1): Move 'R' -> (-1, -1)
(-1, -1): Move 'R' -> (0, -1)
(0, -1): Move '' -> failed

Live Demo on coliru

edited Jun 1, 2019 at 5:47

answered Jun 1, 2019 at 5:24

Scheff's Cat

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5 Comments

πάντα ῥεῖ Over a year ago

I had the same idea to combine X/Y moves into one pair, was just long for a comment :-)

Atul Over a year ago

Need C++11 though

πάντα ῥεῖ Over a year ago

@Atul I don't see why. This should work with c++-98 standards. (unless you mean the using statement, but that could be easily replaced with a typedef)

Scheff's Cat Over a year ago

@Atul It should compile with C++11 as well. (At least it did with g++ -std=c++11.)

Atul Over a year ago

@πάνταῥεῖ Initializing std::map compiles with and above C++11 But anyways since OP has put tag C++11 I believe this should solve his/her problem.

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