查找数组

Question

我正在尝试查找下面所示的以下数组的对角线总和，但每当我调用函数diagsfunc并运行程序时，它都没有给出答案，

我做了一个if语句以确保数组是一个方阵，如果是，它继续调用函数diagsfunc，在那里我找到对角元素的总和但是每当我运行它时都没有打印总和。

下面是函数，main和数组。除了对角线之外，所有其他功能都能正常工作。如果您想知道该文件包含以下数字，前两个数字只是行和列，最后两个数字是用于函数的数组的特定行和列：

该文件包含：

4 4
5.5 7.8 7.8 3.3
2.2 1.1 4.4 7.7
9.9 7.6 4.4 6.6
9.0 4.0 5.0 2.0
2
3

代码：

/*Diagonal function*/
double
diagsfunc (double ** arr, int diagr, int diagc)
{
    int f, g;
    double sum3 = 0;

    for (f=0;f<diagr;++f)
    {
        for (g=0;f<diagc;++g)
        {
            if (f == g)
            {
                sum3 = sum3 + arr[f][g];
            }
        }
    }    

    return(sum3);

}

int
main (void)
{
    int cols, rows, i, j, nrows, ncols;
    double **a;
    double diag;
    FILE * fpointer;
    fpointer = fopen("projectfile.txt", "r");

    fscanf(fpointer, "%d %d", &rows, &cols);

    a = (double **) calloc (rows, sizeof(double *));

    for (i=0; i<rows; ++i)
        a[i] = (double *) calloc (cols, sizeof(double));

    for (i = 0; i < rows; ++i)
        for ( j = 0; j < cols; ++j)
            fscanf(fpointer, "%lf", &a[i][j]);

    for (i = 0; i < rows; ++i){
        for ( j = 0; j < cols; ++j){
            printf("%10.3lf ", a[i][j]);
        }
            puts("");
    }

    fscanf(fpointer, "%d %d", &nrows, &ncols);

    if (rows == cols){
        diag = diagsfunc(a, rows, cols);
        printf("The sum of the diagonal elements is: %.3lf\n", diag);
    } else {
        printf("The array must be square to compute the sum of diagonals\n");
    }
    fclose(fpointer);
    return(0);
}

Answer 1

你做的几乎没有愚蠢的错误，更多，但我列出了只需要一个

1. 循环for (g=0;f<diagc;++g)中使用的错误变量。 它应该是

   for (g = 0;g < diagc; ++g)

2. 找到对角线的总和，你不需要像Pablo指出的2个循环你可以用一个循环本身作为

   for(int i = 0; i < diagr; ++i) { /* if its a square matrix */
           sum3 + = arr[i][i]      
   }
   

完整代码

double diagsfunc (double ** arr, int diagr) {
        int f, g;
        double sum3 = 0;
        for(int i = 0; i < diagr; ++i) {
                sum3 += arr[i][i];
        }
        return sum3;
}
int main (void){
        int cols, rows, i, j, nrows, ncols;
        double **a;
        double diag;
        FILE * fpointer = fopen("projectfile.txt", "r");
        if(fpointer == NULL ) {
                /* put some message */
                return 0;
        }
        fscanf(fpointer, "%d %d", &rows, &cols);
        a = (double **) calloc (rows, sizeof(double *));
        for (i=0; i<rows; ++i)
                a[i] = (double *) calloc (cols, sizeof(double));
        for (i = 0; i < rows; ++i)
                for ( j = 0; j < cols; ++j)
                        fscanf(fpointer, "%lf", &a[i][j]);
        for (i = 0; i < rows; ++i){
                for ( j = 0; j < cols; ++j){
                        printf("%10.3lf ", a[i][j]);
                }
                puts("");
        }
        //rewind(fpointer); /* this you forget */
        //fscanf(fpointer, "%d %d", &nrows, &ncols); /* why this statement ? */
        if (rows == cols){
                diag = diagsfunc(a, rows); /* no need to pass col value as its square matrix, both will be equal */
                printf("The sum of the diagonal elements is: %.3lf\n", diag);
        } else {
                printf("The array must be square to compute the sum of diagonals\n");
        }
        fclose(fpointer);
        return(0);
}

同时检查所有功能的返回值＆amp;学习如何调试代码。