Initial commit

838/838-2.cpp

@@ -0,0 +1,90 @@
+#include <string>
+#include <iostream>
+#include <vector>
+#include <span>
+
+namespace {
+
+enum Dominoes : char {
+    Dot = '.',
+    L = 'L',
+    R = 'R',
+};
+
+using Range = std::tuple<size_t, size_t>;
+using Ranges = std::vector<Range>; 
+
+class Solution {
+    Ranges findRanges(const std::string& dominoes) {
+        Ranges ranges;
+        ranges.reserve(dominoes.size() / 2);
+
+        size_t start = -1;
+
+        for (size_t i = 0; i < dominoes.size(); ++i) {
+            char d = dominoes[i];
+
+            if (d == Dot && start == -1) {
+                start = i;
+            } else if (d != Dot && start != -1) {
+                ranges.emplace_back(start, i);
+                start = -1;
+            }
+        }
+
+        if (start != -1) {
+            ranges.emplace_back(start, dominoes.size());
+        }
+
+        return ranges;
+    }
+    void processRange(const Range& range, std::string& dominoes) {
+        bool left_r = false;
+        bool right_l = false;
+
+        const auto& [start, end] = range;
+
+        if (start > 0 && dominoes[start - 1] == R)
+            left_r = true;
+        if (end < (dominoes.size()) && dominoes[end] == L)
+            right_l = true;
+
+        if (left_r && right_l) {
+            /*
+            * 3 4 5 6 7
+            * . . . . L
+            */
+           auto difference = end - start;
+           auto steps = difference / 2;
+
+           for (auto i = 0; i < steps; ++i) {
+                dominoes[start + i] = R;
+                dominoes[end - 1 - i] = L;
+           }
+        } else if (left_r) {
+            for (auto i = start; i < end; ++i) dominoes[i] = R;
+        } else if (right_l) {
+            for (auto i = start; i < end; ++i) dominoes[i] = L;
+        }
+    }
+    public:
+        std::string pushDominoes(std::string dominoes) {
+            auto ranges = findRanges(dominoes);
+            for (const auto& range : ranges) {
+                auto& [start, end] = range;
+                std::cout << "[" << start << ", " << end << "]\n";
+                processRange(range, dominoes);
+            }
+            return dominoes;
+        }
+    };
+}
+
+#include <gtest/gtest.h>
+
+TEST(P838_2, 1) {
+    std::string input = ".L.R...LR..L..";
+    Solution s;
+    auto result = s.pushDominoes(input);
+    EXPECT_EQ(result, std::string("LL.RR.LLRRLL.."));
+}