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".
就是将一个字符串Z字形排列后再读出的字符串。
可以依次得到各个行的字符串再拼接，比较简单。
我是直接计算的字符串的每位是怎么映射到结果字符串的。都可以。
下面的C代码，已通过。

char* convert(char* s, int numRows) {
    int length=0,i=0,k=0,ansk=0;
    while(s[length]!='\0')length++;
    if(numRows==1||numRows>=length)return s;
    char * ans=(char *)malloc((length+1)*sizeof(char));
    for(i=0;i<numRows;i++)
    {
        k=i;
        if(i==0||i==numRows-1)
        {
            while(length>k&&length>ansk)
            {
                ans[ansk]=s[k];k+=2*(numRows-1);ansk++;
            }
        }
        else
        {
            while(length>k&&length>ansk)
            {
                ans[ansk]=s[k];ansk++;
                k+=2*(numRows-i-1);
                if(k>=length||ansk>=length)break;
                ans[ansk]=s[k];ansk++;
                k+=2*(i);
            }
        }
       // printf("%s\n",ans);
    }
    ans[length]='\0';
    return ans;
}