s0006

include/s0006_zigzag_conversion.hpp

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+#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

src/s0006_zigzag_conversion.cpp

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+#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;
+}

tests/s0006_zigzag_conversion.cpp

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+#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);
+}