From 83c66fc158d37e6d197ccbe11457c9bd363e087e Mon Sep 17 00:00:00 2001
From: Sainnhe Park <i@sainnhe.dev>
Date: Wed, 2 Nov 2022 20:19:54 +0800
Subject: [PATCH] s0006

---
 include/s0006_zigzag_conversion.hpp | 20 +++++++++++
 src/s0006_zigzag_conversion.cpp     | 51 +++++++++++++++++++++++++++++
 tests/s0006_zigzag_conversion.cpp   | 27 +++++++++++++++
 3 files changed, 98 insertions(+)
 create mode 100644 include/s0006_zigzag_conversion.hpp
 create mode 100644 src/s0006_zigzag_conversion.cpp
 create mode 100644 tests/s0006_zigzag_conversion.cpp

diff --git a/include/s0006_zigzag_conversion.hpp b/include/s0006_zigzag_conversion.hpp
new file mode 100644
index 0000000..430a408
--- /dev/null
+++ b/include/s0006_zigzag_conversion.hpp
@@ -0,0 +1,20 @@
+#ifndef S0006_ZIGZAG_CONVERSION
+#define S0006_ZIGZAG_CONVERSION
+
+#include <string>
+
+using namespace std;
+
+class Solution {
+ public:
+  /**
+   * @brief Zigzag Conversion
+   *
+   * @param s the string to be converted
+   * @param numRows rows
+   * @return converted string
+   */
+  string convert(string s, int numRows);
+};
+
+#endif
diff --git a/src/s0006_zigzag_conversion.cpp b/src/s0006_zigzag_conversion.cpp
new file mode 100644
index 0000000..61699d3
--- /dev/null
+++ b/src/s0006_zigzag_conversion.cpp
@@ -0,0 +1,51 @@
+#include "s0006_zigzag_conversion.hpp"
+
+// 简单地找规律
+
+// n = 3
+// 0 4 8 12   2*(n-1) * col
+// 1 3 5 ...  (n-1) * col + 1
+// 2 6 10     2*(n-1) * col + (n-1)
+
+// n = 4
+// 0     6     12   2*(n-1)*col
+// 1   5 7   11     2*(n-1)*col+row, 2*(n-1)*col-row
+// 2 4   8 10       2*(n-1)*col+row, 2*(n-1)*col-row
+// 3     9          2*(n-1)*col + (n-1)
+
+string Solution::convert(string s, int numRows) {
+  string r = "";
+  int l = s.length();
+  if (l == 1 || numRows == 1) {
+    return s;
+  }
+  for (int col = 0; 2 * (numRows - 1) * col < l; col++) {
+    r += s[2 * (numRows - 1) * col];
+  }
+  if (numRows >= 3) {
+    for (int row = 1; row < numRows - 1; row++) {
+      for (int col = 0;; col++) {
+        if (col == 0) {
+          if (2 * (numRows - 1) * col + row < l) {
+          r += s[2 * (numRows - 1) * col + row];
+          }
+        } else {
+          if (2 * (numRows - 1) * col - row < l) {
+            r += s[2 * (numRows - 1) * col - row];
+          } else {
+            break;
+          }
+          if (2 * (numRows - 1) * col + row < l) {
+            r += s[2 * (numRows - 1) * col + row];
+          } else {
+            break;
+          }
+        }
+      }
+    }
+  }
+  for (int col = 0; 2 * (numRows - 1) * col + (numRows - 1) < l; col++) {
+    r += s[2 * (numRows - 1) * col + (numRows - 1)];
+  }
+  return r;
+}
diff --git a/tests/s0006_zigzag_conversion.cpp b/tests/s0006_zigzag_conversion.cpp
new file mode 100644
index 0000000..b9fc807
--- /dev/null
+++ b/tests/s0006_zigzag_conversion.cpp
@@ -0,0 +1,27 @@
+#include "s0006_zigzag_conversion.hpp"
+
+#include <gtest/gtest.h>
+
+TEST(Problem6, Case1) {
+  string s("PAYPALISHIRING");
+  int rows = 3;
+  string r("PAHNAPLSIIGYIR");
+  Solution solution;
+  EXPECT_TRUE(solution.convert(s, rows) == r);
+}
+
+TEST(Problem6, Case2) {
+  string s("PAYPALISHIRING");
+  int rows = 4;
+  string r("PINALSIGYAHRPI");
+  Solution solution;
+  EXPECT_TRUE(solution.convert(s, rows) == r);
+}
+
+TEST(Problem6, Case3) {
+  string s("AB");
+  int rows = 4;
+  string r("AB");
+  Solution solution;
+  EXPECT_TRUE(solution.convert(s, rows) == r);
+}