Create minimum-swaps-to-sort-by-digit-sum.cpp

Author: kamyu104

C++/minimum-swaps-to-sort-by-digit-sum.cpp

@@ -0,0 +1,38 @@
+// Time:  O(nlogr)
+// Space: O(n)
+
+// sort
+class Solution {
+public:
+    int minSwaps(vector<int>& nums) {
+        const auto& total = [](int x) {
+            int result = 0;
+            for (; x; x /= 10) {
+                result += x % 10;
+            }
+            return result;
+        };
+
+        vector<int> idxs(size(nums));
+        iota(begin(idxs), end(idxs), 0);
+        sort(begin(idxs), end(idxs), [&](const auto& i, const auto& j) {
+            return pair(total(nums[i]), nums[i]) < pair(total(nums[j]), nums[j]);
+        });
+        vector<int> i_to_idx(size(idxs), -1);
+        for (int i = 0; i < size(idxs); ++i) {
+            i_to_idx[idxs[i]] = i;
+        }
+        int result = 0;
+        vector<bool> lookup(size(nums));
+        for (int i = 0; i < size(nums); ++i) {
+            int l = 0;
+            while (!lookup[i]) {
+                lookup[i] = true;
+                ++l;
+                i = i_to_idx[i];
+            }
+            result += max(l - 1, 0);
+        }
+        return result;
+    }
+};