面试题4 将一个char数组中的所有空格替换成%20

  public void mySolution(char[] str){
    int last = findLastChar(str);
    if(last==0){
      str = null;
      return;
    }

    int numOfSpace = countSpace(str, last);
    int newLastChar = findNewLastChar(str, numOfSpace);

    int a = last, b = newLastChar;
    while(a>=0){
      if(str[a]!=‘ ‘){
        str[b--] = str[a];
      }else{
        str[b--] = ‘0‘;
        str[b--] = ‘2‘;
        str[b--] = ‘%‘;
      }
      a--;
    }
  }


  private int findLastChar(char[] a){
    int last = 0;
    for(int i=a.length-1; i>=0; i--){
      if(a[i]==‘ ‘) continue;
      last = i;
      break;
    }
    return last;
  }


  private int countSpace(char[] a, int oldLast){
    if(oldLast==0)  return 0;

    int count = 0;
    for(int i=0; i<oldLast; i++)  if(a[i]==‘ ‘) count++;

    return count;
  }


  private int findNewLastChar(char[] a, int spaceCount){
    int last = findLastChar(a);

    if(spaceCount==0) return last;
    else  return last+2*spaceCount;
  }