4 By 4 Skyscrapers Tooling

4_by_4_tooling.js

function solvePuzzle (clues) {
    // The hint says the value
    // that must *at least* be in the adjacent cell.
    // 1 -> 4
    // 2 -> 3, etc.
    
    // Calculate the possible permutations for each score in advance
    // Rotate around in the order of hints, check if there is only
    // one permutation that matches the hint and populated values, if
    // so then populate it.
    let permutationManager = new PuzzlePermutationManager(4);
}

class PuzzlePermutationManager {
  constructor(vectorSize) {
    this.vectorSize = vectorSize;
    this.basisVector = new Array(vectorSize).fill().map((_,i) => { return i + 1 });
    this.cachePermutationsForHints();
  }
  
  cachePermutationsForHints() {
    this._cachedPermutations = PuzzlePermutationManager._generatePermutations(this.basisVector);
    this._cachedHintMatches = this.basisVector.map((hint) => {
      return PuzzlePermutationManager._filterVectorsForHint(hint, this._cachedPermutations)
    });
  }
  
  static _generatePermutations(vector) {
    if ( vector.length == 1) { return [vector] };
    
    let permutations = [];
    for (let i = 0; i < vector.length; i++) {
      let firstValue = vector[0];
      permutations = permutations.concat(
        PuzzlePermutationManager._generatePermutations(vector.slice(1)).map((permutation) => {
          return [firstValue].concat(permutation);
        })
      );
      vector.push(vector.shift());
    }
    
    return permutations;
  }
  
  static _filterVectorsForHint(hint, vectors) {
    return vectors.filter((vector) => {
      let max = 0, increments = 0;
      for(let el of vector) {
        if (el > max) {
          max = el;
          increments++;
        }
      }
      
      return (increments == hint);
    });
  }
}