c语言矩阵运算，关键部分我好像写错了

Question

标注出来的是我不太明白的地方，我写的这个编译没有问题，就是答案很奇怪，能帮忙改改吗？谢了

#include<stdio.h>
int main()
{
    int n,i,j;
    scanf("%d",&n);
    int a[n][n],b[n][n],c[n][n],d[n][n];
    
    for (i=0;i<n;i++)
    {
        for (j=0;j<n;j++)
        {
            scanf("%d",&a[i][j]);
        }
    }
    
    for (i=0;i<n;i++)
    {
        for (j=0;j<n;j++)
        {
            if (a[i][j]==a[j][i])
            {
                printf("YES\n");
                b[j][i]=a[j][i];
                for (j=0;j<n;j++)
                {
                    d[i][j]=a[i][j]*b[j][i];
                    c[i][j]=c[i][j]+d[i][j];
                    printf("%d ",c[i][j]);
                }
            }    
            else
            {
                printf("NO\n");
                b[j][i]=a[j][i];
                d[i][j]=a[i][j]+b[j][i];
                c[i][j]=c[i][j]+d[i][j];
                printf("%d ",c[i][j]);
            }
        }
    }
    printf("\n");
}

Answer 1

供参考：

#include <stdio.h>
#define N 20
int is_symmetricmatrix(int a[][N], int Row,int Col)//判断一个N*N矩阵，是否是对称矩阵，是返回1，否返回0
{
    int i, j, flag;
    for (i = 0, flag = 1; i < Row; i++)
    {
        for (j = 0; j < i; j++)
        {
            if (a[i][j] != a[j][i])
            {
                flag = 0;
                break;
            }
        }
        if (j < i) break;
    }
    if (flag)
        return 1;  
    else
        return 0;  
}
void getTransposeMatrix(int b[][N], int a[][N], int Row, int Col)//矩阵转置
{
    int i, j;
    for (i = 0; i < Row; i++)
        for (j = 0; j < Col; j++)
            b[j][i] = a[i][j];
}
void matrixMul(int a[][N], int b[][N], int c[][N], int Rowa, int Cola, int Colb)//矩阵相乘
{
    int i, j, k;
    for(i=0;i<Rowa;i++)
    {
        for (j = 0; j < Colb; j++)
        {
            for (k = 0; k < Cola; k++)
                c[i][j] += a[i][k] * b[k][j];
        }
    }

}
void matrixAdd(int a[][N], int b[][N], int c[][N], int Rowa, int Cola)//矩阵相加
{
    int i, j;
    for (i = 0; i < Rowa; i++)
        for (j = 0; j < Cola; j++)
            c[i][j] = a[i][j] + b[i][j];
}
void printmatrix(int a[][N], int Row, int Col)
{
    int i, j;
    for (i = 0; i < Row; i++){
        for (j = 0; j < Col; j++)
        {
            printf("%d ", a[i][j]);
        }
        printf("\n");
    }
}
int main()
{
    int a[N][N] = { 0 }, b[N][N] = { 0 }, c[N][N] = {0}, i, j, n = 3;

    scanf("%d", &n);
    for (i = 0; i < n; i++)
        for (j = 0; j < n; j++)
            scanf("%d", &a[i][j]);
    if (is_symmetricmatrix(a, n, n))
    {
        printf("YES\n");
        getTransposeMatrix(b, a, n, n);
        matrixMul(a, b, c, n, n, n);
        printmatrix(c, n, n);
    }
    else{
        printf("NO\n");
        getTransposeMatrix(b, a, n, n);
        matrixAdd(a, b, c, n, n);
        printmatrix(c, n, n);
    }
    return 0;
}