如果我要写下面一段代码:
int ret=0; if(flag1) ret+=a1; if(flag2) ret+=a2; if(flag3) ret+=a3; f=ret;
怎么用数学公式表达出来?
瞎猜的: f=∑{a1flag1a2flag2a3flag3\begin{aligned} f=\sum\left\{ \begin{array}{l} a_1 & flag_1 \\ a_2 & flag_2\\ a_3 & flag_3 \end{array} \right. \end{aligned} f=∑⎩⎨⎧a1a2a3flag1flag2flag3