normalize()错误

struct vecto3{float x;float y;float z;vecto3(){x=y=z=0;}float vecLength(){return sqrt(x*x+y*y+z*z);}void normalize(){const float temp=vecLength();if (temp!=0){x=x/temp;y=y/temp;z=z/temp;}}}

vecto3 normalize(vecto3 & vv){ float  vecLength=sqrt(vv.x*vv.x+vv.y*vv.y+vv.z*vv.z);if (vecLength!=0){vv.x=vv.x/vecLength;vv.y=vv.y/vecLength;vv.z=vv.z/vecLength;}return vv;}

struct vecto3{float x;float y;float z;vecto3(float xx,float yy,float zz){x=xx;y=yy;z=zz;}float vecLength(){return sqrt(x*x+y*y+z*z);}void normalize(){if ( vecLength()!=0){x=x/vecLength();y=y/vecLength();z=z/vecLength();}}}

以上三个 normalize()有什么不同？

注：最后一个是错的！