LeetCode 006 ZigZag Conversion

【题目】

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".

【题意】

题意是按之字形将元字符串组织成n行，然后将这n行字符串拼接起来输出

【思路】

    设置一个转向变量direction
    两个区间上下界变量  bottomBound=1, topBound=n
    之字行计数变量 pCount， 当计数指针指向上下边界时，转向变量变向

【代码】

class Solution {
public:
    string convert(string s, int nRows) {
		int sLen=s.length();
		if(sLen==0)return "";   //考虑字符串为空的情况
		if(nRows==1)return s;   //考虑nRows=1的情况
		int bottomBound=0;
		int topBound=nRows-1;
		int pCount=0;
		bool direction=false;
		vector<string> rowStrs(nRows, "");
		for(int i=0; i<sLen; i++){
		    rowStrs[pCount]+=s[i];
		    if(pCount==bottomBound){
		        direction=true;
		    }
		    else if(pCount==topBound){
		        direction=false;
		    }
		    
		    if(direction)pCount++;
		    else pCount--;
		}
		string resultStr="";            //拼接字符串
		for(int i=0; i<nRows; i++)
		    resultStr+=rowStrs[i];
		return resultStr;
    }
};