<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>

// class SegmentTree {
//     private: 
//         vector<int> seg;
//         int n;

//     public:

//         SegmentTree(int n) {
//             seg.resize(4 * n, 0);
//             this->n = n;
//         }


// };

class Solution {
public:
    string minInteger(string num, int k) {
        string ans = "";
        int pos, dis;
        vector<queue<int>> digitPos(10);  
        set<int> storeUsedInd;

        // store the indices of all digits
        for(int i=0;i<num.length();i++) {
            digitPos[num[i] - '0'].emplace(i);
        }

        // for(int i=0;i<=9;i++) {
        //     cout<<digitPos[]
        // }

        for(int i=0;i<num.length();i++) {
            for(int j=0;j<=9;j++) {
                if(!digitPos[j].empty()) {
                    pos = digitPos[j].front();
                    // cout<<i<<" "<<j<<" "<<pos<<endl;
                    dis = distance(storeUsedInd.upper_bound(pos), storeUsedInd.end());
                    
                    if(pos + dis - i <= k) {
                        ans += (j + '0');
                        digitPos[j].pop();
                        storeUsedInd.insert(pos);
                        k -= (pos + dis - i);
                        break;
                    }   
                }
            }
        }

        for(int i=0;i<num.length();i++) {
            if(storeUsedInd.find(i) == storeUsedInd.end()) {
                ans += num[i];
            }
        }

        return ans;
    }
};
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