c语言求定3*3矩阵中,主副对角线上所有元素之和答:int main() { int i,a[N][N] = {1,2,3,4,5,6,7,8,9};int major_diagonal = 0,assist_diagonal = 0;for(i = 0; i < N; ++i) { major_diagonal += a[i][i];assist_diagonal += a[i][N - 1 - i];} printf("主要对角线的和为:%d\n",major_diagonal);printf("...