Leetcode 6. ZigZag Conversion（找规律，水题）

6. ZigZag Conversion

Medium

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 s, int numRows);

Example 1:

Input: s = "PAYPALISHIRING", numRows = 3
Output: "PAHNAPLSIIGYIR"

Example 2:

Input: s = "PAYPALISHIRING", numRows = 4
Output: "PINALSIGYAHRPI"
Explanation:

P     I    N
A   L S  I G
Y A   H R
P     I

(之字型）

class Solution {
public:
    string convert(string s, int numRows) {
        int len = s.length();
        string ans;
        if(numRows==1) return s;
        for(int i = 0;i < numRows; i++){
            int left = (numRows-1-i)*2;
            int right = (i)*2;
            int cnt = i;
            int flag = 1;
            while(cnt < len){
                flag = (flag+1)%2;
                if((left==0 && flag==0)||(right==0&&flag==1)) continue;
                ans+=s[cnt];
                if(flag==0) cnt = cnt+left;
                else cnt = cnt+right;
            }
        }
        return ans;
    }
};