我尝试了这段代码,但出了点问题
for (i = 0; i < row1; i++) {
for (j = 0; j < col2; j++)
suma = 0;
for (l = 0; l < row2; l++)
suma += a[i][l] * bt[l][j];
c[i][j] = suma;
}
printf("\nMultiplication of 2 matrices:\n");
for (i = 0; i < row1; i++) {
for (j = 0; j < col2; j++)
printf("%2d", c[i][j]);
printf("\n");
}
当我调试它时,它会在行和列中打印出随机数(类似于-895473)
答案 0 :(得分:5)
缺少牙箍。
for (i = 0; i < row1; i++) {
for (j = 0; j < col2; j++) { // added brace
suma = 0;
for (l = 0; l < row2; l++) { // added brace
suma += a[i][l] * bt[l][j];
} // added brace
c[i][j] = suma;
} // added brace
}
内部的大括号不是严格必要但是如果你总是使用大括号,你将来不太可能犯这个特别的错误。
没有大括号,它看起来像这样,正确缩进:
for (i = 0; i < row1; i++) {
for (j = 0; j < col2; j++)
suma = 0;
// Note that j = col2, which means that we are accessing
// array elements out of bounds, which is an error.
for (l = 0; l < row2; l++)
suma += a[i][l] * bt[l][j];
c[i][j] = suma;
}
这显然是错误的。另一种使错误不太可能的方法是在循环中移动变量:
for (int i = 0; i < row1; i++) {
for (int j = 0; j < col2; j++) {
double suma = 0;
for (int l = 0; l < row2; l++) {
suma += a[i][l] * bt[l][j];
}
c[i][j] = suma;
}
}
这样,如果删除大括号,则会收到错误,因为未定义j
。 (这在C90中不起作用,但现在这是古老的历史。)