1. Combination Sum Add to List QuestionEditorial Solution My Submissions
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   Difficulty: Medium
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   Given a set of candidate numbers (C) and a target number (T), find all unique combinations in C where the candidate numbers sums to T.

The same repeated number may be chosen from C unlimited number of times.

Note:
All numbers (including target) will be positive integers.
The solution set must not contain duplicate combinations.
For example, given candidate set [2, 3, 6, 7] and target 7,
A solution set is:
[
[7],
[2, 2, 3]
]
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思路描述
先用快速排序進行排序。
藉助有序字典，從大值到小值進行廣度優先遍歷演算法，記錄符合remainder為0 的路徑。

/**
 * @param {number[]} candidates
 * @param {number} target
 * @return {number[][]}
 */
var g_result = [];
var g_target = [];
var g_candidates ;
var combinationSum = function(candidates, target) {

    g_result = [];
    g_target = target;

    qSort(candidates,0
 
,candidates.length-1);
    g_candidates = candidates;

    //genCombination(target, []);
    genCombination1(target, [], g_candidates.length-1);//當陣列變成有序之後，利用有序可以去掉重複的遍歷路徑


    return g_result;
};


var qSort= function(array , low , high)
{  
    if (low < high)
    {
         var pivotIndex = partition(array , low ,high);
         qSort(array, low , pivotIndex -1);
         qSort(array, pivotIndex + 1 , high);
    }
}

var partition =  function(array , low , high)
{
    var pivot = array[low];
    if(low > high)
    {
       while(low<high && pivot < array[high] ){ high--;}
       if(low < high) array[low++] = array[high];

       while(low<hight && pivot > array[low] ){ low++;}
       if(low < high )array[high++] = array[low];

    }
    array[low] = pivot;
    return low;
}

var genCombination1 = function(remainder , combination , maxIndex )
{
    if(remainder < 0)
    {
        return
    }
    else if (remainder > 0)
    {

        for(var  i = maxIndex ; i>= 0  ; i--)//這是遍歷的不一樣的地方。
        {
          var newcomb = combination.concat();
          newcomb.push(g_candidates[i]);
          genCombination1( remainder - g_candidates[i] ,newcomb,i );
        }
        return
    }
    else
    {
       g_result.push(combination);

    }

}


var genCombination = function(remainder , combination  )
{
    console.log("remainder:"+remainder+" combination"+combination);
    if(remainder < 0)
    {
        return
    }
    else if (remainder > 0)
    {

        for(var  i = 0 ; i < g_candidates.length ; i++)
        {
          var newcomb = combination.concat();
          newcomb.push(g_candidates[i]);
          genCombination( remainder - g_candidates[i] ,newcomb);
        }
        return
    }
    else
    {
       g_result.push(combination);

    }
}