递归回溯数独求解问题，c++

这是我第一次在低级课程中将递归作为作业来处理。我在互联网上四处寻找，似乎找不到任何人使用与我提出的方法类似的方法(这可能说明了为什么它不起作用)。错误是std::__copy_move...的分割错误，我假设这是c++ STL中的一些东西。我的代码如下:

bool sudoku::valid(int x, int y, int value)
{
    if (x < 0) {cerr << "No valid values exist./n";}
    if (binary_search(row(x).begin(), row(x).end(), value))
        {return false;}                 //if found in row x, exit, otherwise:
    else if (binary_search(col(y).begin(), col(y).end(), value))
        {return false;}                 //if found in col y, exit, otherwise:
    else if (binary_search(box((x/3), (y/3)).begin(), box((x/3), (y/3)).end(), value))
        {return false;}                 //if found in box x,y, exit, otherwise:
    else
        {return true;}                  //the value is valid at this index
}
int sudoku::setval(int x, int y, int val)
{
    if (y < 0 && x > 0) {x--; y = 9;}   //if y gets decremented past 0 go to previous row.
    if (y > 8) {y %= 9; x++;}           //if y get incremented past 8 go to next row.
    if (x == 9) {return 0;}             //base case, puzzle done.
    else {
        if (valid(x,y,val)){            //if the input is valid
            matrix[x][y] = val;         //set the element equal to val
            setval(x,y++,val);          //go to next element
        }
        else {
            setval(x,y,val++);          //otherwise increment val
            if(val > 9) {val = value(x,y--); setval(x,y--,val++); }
        }                               //if val gets above 9, set val to prev element,  
    }                                   //and increment the last element until valid and start over
}