6. ZigZag Conversion

  1 char* convert(char* s, int numRows) {
  2 
  3     if(numRows == 1) {
  4         return s;
  5     }
  6 
  7     char *p = (char *) malloc (sizeof(char) * 1000);
  8     char *q = s;
  9     int len = 0;
 10     while(*q != ‘\0‘) {
 11         len++;
 12         q++;
 13     }
 14 
 15     int i=0;
 16     int seq = 0;                /* used to record current write position */
 17     int circle = 2 * numRows - 2;
 18     for(i=0; i<numRows && i<len; i++) {
 19         int a = i;
 20         while(a<len) {
 21             *(p+seq) = s[a];
 22             seq++;
 23             if(0 <= a%circle && a%circle < circle/2) {
 24                 a =  (a/circle * circle + circle/2)*2 - a;
 25             } else {
 26                 a = (a/circle + 1) * circle * 2 - a;
 27             }
 28         }
 29     }
 30     *(p+seq) = ‘\0‘;
 31     return p;
 32 
 33 }