左填充

代码：

class StringUtils {
public:
/**
* @param originalStr the string we want to append to
* @param size the target length of the string
* @param padChar the character to pad to the left side of the string
* @return a string
*/
static string leftPad(string& originalStr, int size, char padChar=' ') {
// Write your code here
int len = originalStr.size();

if( len < size ) {
string add( size - len, padChar );
originalStr = add + originalStr;
}

return originalStr;
}
};