<p>You are given a string <code>num</code> representing <strong>the digits</strong> of a very large integer and an integer <code>k</code>. You are allowed to swap any two adjacent digits of the integer <strong>at most</strong> <code>k</code> times.</p>

<p>Return <em>the minimum integer you can obtain also as a string</em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2020/06/17/q4_1.jpg" style="width: 500px; height: 40px;" />
<pre>
<strong>Input:</strong> num = &quot;4321&quot;, k = 4
<strong>Output:</strong> &quot;1342&quot;
<strong>Explanation:</strong> The steps to obtain the minimum integer from 4321 with 4 adjacent swaps are shown.
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> num = &quot;100&quot;, k = 1
<strong>Output:</strong> &quot;010&quot;
<strong>Explanation:</strong> It&#39;s ok for the output to have leading zeros, but the input is guaranteed not to have any leading zeros.
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> num = &quot;36789&quot;, k = 1000
<strong>Output:</strong> &quot;36789&quot;
<strong>Explanation:</strong> We can keep the number without any swaps.
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= num.length &lt;= 3 * 10<sup>4</sup></code></li>
	<li><code>num</code> consists of only <strong>digits</strong> and does not contain <strong>leading zeros</strong>.</li>
	<li><code>1 &lt;= k &lt;= 10<sup>9</sup></code></li>
</ul>

void update(vector<int> &segtree,int idx,int l,int r,int i,int v)
{
    if(l==r)
    {
        segtree[idx]=v;
        return;
    }
    int mid=(l+r)/2;
    if(i<=mid)
    update(segtree,2*idx+1,l,mid,i,v);
    else
    update(segtree,2*idx+2,mid+1,r,i,v);
    segtree[idx]=(segtree[2*idx+1]+segtree[2*idx+2]);
 
}
int find(vector<int> &segtree,int idx,int l,int r,int a,int b)
{
    if(l>b||r<a)
    return 0;
    if(a<=l&&r<=b)
    return segtree[idx];
    int mid=(l+r)/2;
    return (find(segtree,2*idx+1,l,mid,a,b)+find(segtree,2*idx+2,mid+1,r,a,b));
}

class Solution {
public:
    string minInteger(string num, int k) {
        int n=num.length();
        string ans="";
        stack<int> s[10];
        for(int i=n-1;i>=0;i--)
        s[num[i]-'0'].push(i);
        vector<int> segtree(4*n,0);
        for(int i=0;i<n;i++)
        update(segtree,0,0,n-1,i,1);
        for(int i=0;i<n;i++)
        {
            for(int j=0;j<10;j++)
            {
                if(s[j].size()==0)
                continue;
                int idx=s[j].top();
                int val=find(segtree,0,0,n-1,0,idx-1);
                if(val<=k)
                {
                    ans+=(j+'0');
                    k-=val;
                    update(segtree,0,0,n-1,idx,0);
                    s[j].pop();
                    break;
                }

            }
        }
        return ans;
    }
};
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