【Leetcode】ZigZag Conversion
The string "PAYPALISHIRING"
is written in a zigzag pattern on a given number of rows like this: (you may want to display this pattern in a fixed font for better legibility)
P A H N A P L S I I G Y I R
And then read line by line: "PAHNAPLSIIGYIR"
Write the code that will take a string and make this conversion given a number of rows:
string convert(string text, int nRows);
convert("PAYPALISHIRING", 3)
should return "PAHNAPLSIIGYIR"
.
模拟题,要特别注意nRows为1时的特殊情况处理。
1 class Solution { 2 public: 3 string convert(string s, int nRows) { 4 vector<string> v(nRows); 5 string ret; 6 bool down = true; 7 int n = s.size(); 8 int k = 0; 9 for (int i = 0; i < n; ++i) { 10 if (down) { 11 v[k].push_back(s[i]); 12 ++k; 13 if (k == nRows) { 14 k = max(0, nRows - 2); 15 if (k > 0) { 16 down = false; 17 } 18 } 19 } else { 20 v[k].push_back(s[i]); 21 --k; 22 if (k == 0) { 23 down = true; 24 } 25 } 26 } 27 for (int i = 0; i < nRows; ++i) { 28 int m = v[i].size(); 29 for (int j = 0; j < m; ++j) { 30 ret.push_back(v[i][j]); 31 } 32 } 33 return ret; 34 } 35 };
或者用找规律的方法,但是也需要单独考虑nRow为1的情况。
1 class Solution { 2 public: 3 string convert(string s, int nRows) { 4 if (nRows < 2) return s; 5 string ret; 6 int step = 2 * nRows - 2, n = s.size(); 7 for (int i = 0; i < nRows; ++i) { 8 for (int j = i; j < n; j += step) { 9 ret.push_back(s[j]); 10 if (i != 0 && i != nRows - 1 && j + 2 * (nRows - i - 1) < n) { 11 ret.push_back(s[j + 2 * (nRows - i - 1)]); 12 } 13 } 14 } 15 return ret; 16 } 17 };