problems(cpp): add „1657. Determine if Two Strings Are Close“

Signed-off-by: Matej Focko <mfocko@redhat.com>

grind75/week-1/two-sum.swift

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+../../problems/two-sum.swift

grind75/week-1/valid-parentheses.swift

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+../../problems/valid-parentheses.swift

problems/determine-if-two-strings-are-close.cpp

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+#include <algorithm>
+#include <array>
+#include <string>
+
+class Solution {
+    using freq_t = std::array<std::size_t, 26>;
+
+    freq_t freqs(const std::string& word)
+    {
+        freq_t f { 0 };
+
+        for (auto c : word) {
+            f[c - 'a']++;
+        }
+
+        return f;
+    }
+
+    int mask(const freq_t& f)
+    {
+        int m = 0;
+
+        for (auto c : f) {
+            m = (m << 1) | (c > 0);
+        }
+
+        return m;
+    }
+
+public:
+    bool closeStrings(std::string word1, std::string word2)
+    {
+        auto f1 = freqs(word1);
+        auto m1 = mask(f1);
+        std::sort(f1.begin(), f1.end());
+
+        auto f2 = freqs(word2);
+        auto m2 = mask(f2);
+        std::sort(f2.begin(), f2.end());
+
+        return m1 == m2 && f1 == f2;
+    }
+};

problems/two-sum.swift

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+class Solution {
+    func twoSum(_ nums: [Int], _ target: Int) -> [Int] {
+        var encountered: [Int: Int] = [:]
+
+        for (i, x) in nums.enumerated() {
+            if encountered[target - x] != nil {
+                return [encountered[target - x]!, i]
+            }
+
+            encountered[x] = i
+        }
+
+        return []
+    }
+}

problems/valid-parentheses.swift

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+class Solution {
+    func isValid(_ s: String) -> Bool {
+        var stack: [Character] = []
+
+        for c in s {
+            switch c {
+                case "(":
+                    stack.append(")")
+                case "{":
+                    stack.append("}")
+                case "[":
+                    stack.append("]")
+                default:
+                    if (stack.popLast() != c) {
+                        return false
+                    }
+            }
+        }
+
+        return stack.isEmpty
+    }
+}