2017-09-08 LeetCode_006 ZigZag Conversion

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本文介绍了一种将字符串按ZigZag形式排列再逐行读取的算法实现。该算法接受一个字符串和行数作为输入参数，返回转换后的字符串。通过计算字符串长度、行数及模式周期等关键信息，确保正确处理边界情况。

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6. 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".

solution:

class Solution {
public:
    string convert(string s, int numRows) {
        string ans;
        int l = s.length(), n = numRows;
        int m = (n == 1 ? 1 : 2*n-2);
        int k = l/m, r = l%m;
        for (int i = 0; i < n; i++)
            if (i == 0) {
                int max = (r == 0 ? k : k+1);
                for (int j = 0; j < max; j++) ans += s[j*m];
            } else if (i == n-1) {
                int max = (r <= n-1 ? k : k+1);
                for (int j = 0; j < max; j++) ans += s[j*m+n-1];
            } else {
                int max;
                if (r <= i) max = 2*k;
                else if (i < r && r <= m-i) max = 2*k+1;
                else max = 2*k+2;
                for (int j = 0; j < max; j++)
                    if (j%2 == 0) ans += s[(int)(j/2)*m+i];
                    else ans += s[(int)(j/2)*m+m-i];
            }
        return ans;
    }

};