Sync LeetCode submission Runtime - 434 ms (62.29%), Memory - 216.4 MB (46.19%)

Author: koralkulacoglu

LeetCode/3847-minimum-swaps-to-sort-by-digit-sum/README.md

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+<p>You are given an array <code>nums</code> of <strong>distinct</strong> positive integers. You need to sort the array in <strong>increasing</strong> order based on the sum of the digits of each number. If two numbers have the same digit sum, the <strong>smaller</strong> number appears first in the sorted order.</p>
+
+<p>Return the <strong>minimum</strong> number of swaps required to rearrange <code>nums</code> into this sorted order.</p>
+
+<p>A <strong>swap</strong> is defined as exchanging the values at two distinct positions in the array.</p>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+
+<div class="example-block">
+<p><strong>Input:</strong> <span class="example-io">nums = [37,100]</span></p>
+
+<p><strong>Output:</strong> <span class="example-io">1</span></p>
+
+<p><strong>Explanation:</strong></p>
+
+<ul>
+	<li>Compute the digit sum for each integer: <code>[3 + 7 = 10, 1 + 0 + 0 = 1] &rarr; [10, 1]</code></li>
+	<li>Sort the integers based on digit sum: <code>[100, 37]</code>. Swap <code>37</code> with <code>100</code> to obtain the sorted order.</li>
+	<li>Thus, the minimum number of swaps required to rearrange <code>nums</code> is 1.</li>
+</ul>
+</div>
+
+<p><strong class="example">Example 2:</strong></p>
+
+<div class="example-block">
+<p><strong>Input:</strong> <span class="example-io">nums = [22,14,33,7]</span></p>
+
+<p><strong>Output:</strong> <span class="example-io">0</span></p>
+
+<p><strong>Explanation:</strong></p>
+
+<ul>
+	<li>Compute the digit sum for each integer: <code>[2 + 2 = 4, 1 + 4 = 5, 3 + 3 = 6, 7 = 7] &rarr; [4, 5, 6, 7]</code></li>
+	<li>Sort the integers based on digit sum: <code>[22, 14, 33, 7]</code>. The array is already sorted.</li>
+	<li>Thus, the minimum number of swaps required to rearrange <code>nums</code> is 0.</li>
+</ul>
+</div>
+
+<p><strong class="example">Example 3:</strong></p>
+
+<div class="example-block">
+<p><strong>Input:</strong> <span class="example-io">nums = [18,43,34,16]</span></p>
+
+<p><strong>Output:</strong> <span class="example-io">2</span></p>
+
+<p><strong>Explanation:</strong></p>
+
+<ul>
+	<li>Compute the digit sum for each integer: <code>[1 + 8 = 9, 4 + 3 = 7, 3 + 4 = 7, 1 + 6 = 7] &rarr; [9, 7, 7, 7]</code></li>
+	<li>Sort the integers based on digit sum: <code>[16, 34, 43, 18]</code>. Swap <code>18</code> with <code>16</code>, and swap <code>43</code> with <code>34</code> to obtain the sorted order.</li>
+	<li>Thus, the minimum number of swaps required to rearrange <code>nums</code> is 2.</li>
+</ul>
+</div>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li><code>1 &lt;= nums.length &lt;= 10<sup>5</sup></code></li>
+	<li><code>1 &lt;= nums[i] &lt;= 10<sup>9</sup></code></li>
+	<li><code>nums</code> consists of <strong>distinct</strong> positive integers.</li>
+</ul>

LeetCode/3847-minimum-swaps-to-sort-by-digit-sum/solution.cpp

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+struct Num {
+    int val;
+    int digitSum;
+
+    Num(int val) : val(val), digitSum(0) {
+        int temp = val;
+        while (temp) {
+            digitSum += temp % 10;
+            temp /= 10;
+        }
+    }
+
+    bool operator<(const Num& other) const {
+        if (digitSum < other.digitSum) return true;
+        if (digitSum > other.digitSum) return false;
+        return val < other.val;
+    }
+};
+
+class Solution {
+public:
+    int minSwaps(vector<int>& nums) {
+        int n = nums.size();
+        unordered_map<int, int> loc;
+        for (int i=0; i<n; i++) loc[nums[i]] = i;
+        vector<Num> a(nums.begin(), nums.end());
+        sort(a.begin(), a.end());
+
+        int ans = 0;
+        for (int i=0; i<n; i++) {
+            if (nums[i] != a[i].val) {
+                int correctVal = a[i].val;
+                int oldIdx = loc[correctVal];
+                int currentVal = nums[i];
+                loc[currentVal] = oldIdx;
+                loc[correctVal] = i;
+                swap(nums[i], nums[oldIdx]);
+                ans++;
+            }
+        }
+
+        return ans;
+    }
+};