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".
解法:
先从上向下扫描,即0~nRows-1,,后扫斜对角线,即gap~1。
string convert(string s, int nRows)
{
if(nRows == 1) return s;
string res[nRows];
int i = 0, j, gap = nRows-2;
while(i < s.size())
{
for(j = 0; i < s.size() && j < nRows; ++j)
res[j] += s[i++];
for(j = gap; i < s.size() && j > 0; --j)
res[j] += s[i++];
}
string str = "";
for(i = 0; i < nRows; ++i)
str += res[i];
return str;
}