是否可以使用break函数退出几个嵌套的for循环?
如果是,你会怎么做呢?你还能控制刹车出多少圈吗?
是否可以使用break函数退出几个嵌套的for循环?
如果是,你会怎么做呢?你还能控制刹车出多少圈吗?
当前回答
Goto对于打破嵌套循环非常有用
for (i = 0; i < 1000; i++) {
for (j = 0; j < 1000; j++) {
for (k = 0; k < 1000; k++) {
for (l = 0; l < 1000; l++){
....
if (condition)
goto break_me_here;
....
}
}
}
}
break_me_here:
// Statements to be executed after code breaks at if condition
其他回答
Breaking out of a for-loop is a little strange to me, since the semantics of a for-loop typically indicate that it will execute a specified number of times. However, it's not bad in all cases; if you're searching for something in a collection and want to break after you find it, it's useful. Breaking out of nested loops, however, isn't possible in C++; it is in other languages through the use of a labeled break. You can use a label and a goto, but that might give you heartburn at night..? Seems like the best option though.
bool found = false;
for(int i=0; i < m; ++i){
for(int j=0; j < n; ++j)
if(grid[i][j] == '*'){
q.push(make_pair(i,j));
found = true;
break;
}
if(found)
break;
}
一个使用goto和标签跳出嵌套循环的代码示例:
for (;;)
for (;;)
goto theEnd;
theEnd:
其他语言如PHP接受break参数(即break 2;)来指定你想要跳出的嵌套循环级别的数量,但c++不接受。你必须使用一个在循环之前设置为false的布尔值,如果你想中断,在循环中设置为true,在嵌套循环之后加上一个条件中断,检查布尔值是否设置为true,如果是则中断。
break语句终止它出现的最近的封闭do、for、switch或while语句的执行。控制权转移到终止语句后面的语句。
从msdn。