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

 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;
    }

其他回答

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

打破嵌套循环的另一种方法是将两个循环分解成一个单独的函数,并在希望退出时从该函数返回。

当然,这也引发了另一个争论,即是否应该显式地从函数的任何地方返回,而不是在函数的末尾。

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。

这个怎么样?

for(unsigned int i=0; i < 50; i++)
{
    for(unsigned int j=0; j < 50; j++)
    {
        for(unsigned int k=0; k < 50; k++)
        {
            //Some statement
            if (condition)
            {
                j=50;
                k=50;
            }
        }
    }
}

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.