1)
#include <stdio.h>
#include <stdlib.h>
#include <conio.h>
const int m = 10, n = 20;
int random(int r)
{
    return rand() % r;
}
int main()
{
    int i, j, A[m][n], temp;
    for (i = 0; i < m; i++)
        for (j = 0; j < n; j++)
            A[i][j] = random(20);
    for (i = 0; i < m; i++)
    {
        for (j = 0; j < n; j++)
            printf("%4d", A[i][j]);
        printf("\n");
    }
    for (i = 0; i < m; i += 2)
        for (j = 0; j < n; j++)
        {
            temp = A[i][j];
            A[i][j] = A[i + 1][j];
            A[i + 1][j] = temp;
        }
    printf("\n");
    for (i = 0; i < m; i++)
    {
        for (j = 0; j < n; j++)
            printf("%4d", A[i][j]);
        printf("\n");
    }
}
-----------------------------------------------------
2)
#include <stdio.h>
#include <stdlib.h>
const int n = 5;
int main()
{
    float A[n][n], summ = 0, a = 5.0;
    int i, j, j1;
    for (i = 0; i < n; i++)
        for (j = 0; j < n; j++)
            A[i][j] = (float)rand() / (float)(RAND_MAX)*a;
    for (i = 0; i < n; i++)
    {
        for (j = 0; j < n; j++)
            printf("%10f", A[i][j]);
        printf("\n");
    }
    printf("\n");
    for (i = 0; i < n; i++)
    {
        for (j = 0; j < n; j++)
            summ += A[i][j];
        for (j1 = 0; j1 < n; j1++)
            A[i][j1] /= summ;
        summ = 0;
    }
    for (i = 0; i < n; i++)
    {
        for (j = 0; j < n; j++)
            printf("%10f", A[i][j]);
        printf("\n");
    }
}
---------------------------------------------------------
3)
#include <stdio.h>
#include <stdlib.h>
const int n = 5;
int random(int r)
{
    return rand() % r;
}
int main()
{
    int i, j, A[n][n], B[n][n];
    for (i = 0; i < n; i++)
        for (j = 0; j < n; j++)
            A[i][j] = random(10);
    for (i = 0; i < n; i++)
    {
        for (j = 0; j < n; j++)
            printf("%4d", A[i][j]);
        printf("\n");
    }
    printf("\n");
    for (i = 0; i < n; i++)
        for (j = 0; j < n; j++)
            B[i][j] = A[j][i];
    for (i = 0; i < n; i++)
    {
        for (j = 0; j < n; j++)
            printf("%4d", B[i][j]);
        printf("\n");
    }
}
---------------------------------------------------------
4)
#include <stdio.h>
#include <stdlib.h>
const int n = 3;
int random(int r)
{
    return rand() % r;
}
int main()
{
    int A[n][n], i, j, summ = 0, flag = 0, count = 0, S[6], c = 0;
    while (flag != 1)
    {
        for (i = 0; i < n; i++)
        {
            for (j = 0; j < n; j++)
                A[i][j] = random(10);
            count += 1;
        }
        for (i = 0; i < n; i++)
        {
            for (j = 0; j < n; j++)
                summ += A[i][j];
            S[c] = summ;
            c += 1;
            summ = 0;
        }
        for (j = 0; j < n; j++)
        {
            for (i = 0; i < n; i++)
                summ += A[i][j];
            S[c] = summ;
            c += 1;
            summ = 0;
        }
        c = 0;
        for (i = 0; i < 6; i++)
        {
            if (S[i] == S[i + 1])
                c += 1;
        }
        if (c == 5)
            flag = 1;
        else
            c = 0;
    }
    printf("%d", count);
}