add: 220427 [cpp]

cpp/2204/220427.cpp

@@ -0,0 +1,57 @@
+#include <vector>
+#include <string>
+#include <algorithm>
+#include <unordered_map>
+#include <iostream>
+#include <functional>
+
+/**
+ * 1202. Smallest String With Swaps
+ * You are given a string s, and an array of pairs of indices in the string pairs where pairs[i] = [a, b] indicates 2 indices(0-indexed) of the string.
+ * You can swap the characters at any pair of indices in the given pairs any number of times.
+ * Return the lexicographically smallest string that s can be changed to after using the swaps.
+ */
+
+class Solution {
+public:
+	static std::string smallestStringWithSwaps(const std::string& s, const std::vector<std::vector<int>>& pairs) {
+		const int n = s.length();
+
+		// Disjoint Set
+		int* mother = new int[n];
+		for (int i = 0; i < n; ++i)
+			mother[i] = i;
+
+		std::function<int(int)> Find = [&](int x) { return mother[x] == x ? x : mother[x] = Find(mother[x]); };
+		auto Union = [&](int x, int y) { mother[Find(x)] = Find(y); };
+
+		for (const auto& p : pairs)
+			Union(p[0], p[1]);
+
+		std::unordered_map<int, std::vector<int>> m;
+		for (int i = 0; i < n; ++i)
+			m[Find(i)].push_back(i);
+
+		std::string ans = s;
+		for (const auto& [i, v] : m) {
+			if (v.size() <= 1)
+				continue;
+
+			int cnt[26]{};
+			for (int idx : v)
+				++cnt[s[idx] - 'a'];
+
+			for (int ptr = 0, j = 0; ptr < 26; ++ptr)
+				while (cnt[ptr]--)
+					ans[v[j++]] = 'a' + ptr;
+		}
+
+		return ans;
+	}
+};
+
+int main() {
+	auto ans = Solution::smallestStringWithSwaps("dcab", {{0,3},{1,2}});
+	std::cout << ans << "\n";
+	return 0;
+}