C_TA_Website/source/_posts/answer7.md

---
title: 第七次作业（答案）
date: 2020-11-27 10:53:14
tags:
---

# 交换宏

```C
#include <stdio.h>

#define SWAP(a, b)        \
    {                     \
        typeof(a) _t = a; \
        a = b;            \
        b = _t;           \
    }

int main()
{
    int a, b;
    printf("请输入a和b:\n");
    printf("a = ");
    scanf("%d", &a);
    printf("b = ");
    scanf("%d", &b);
    SWAP(a, b);
    printf("\n交换后的结果：\na = %d\nb = %d\n", a, b);
    return 0;
}
```

# 排序与查找

```C
#include <stdio.h>
#include <stdlib.h>
#include <time.h>

#define LEN 10

void swap(int *a, int i, int j)
{
    int tmp = a[i];
    a[i] = a[j];
    a[j] = tmp;
}

void bubble_sort(int *a, int n)
{
    int done = 0;
    for (int i = 0; i < n - 1; ++i) {
        if (done)
            return;
        done = 1;
        for (int j = 0; j < n - 1 - i; ++j) {
            if (a[j] > a[j + 1]) {
                swap(a, j, j + 1);
                done = 0;
            }
        }
    }
}

void rand_array(int *a, int n)
{
    for (int i = 0; i < n; ++i) {
        int tmp = rand() % 20 + 1;
        a[i] = tmp;
    }
}

void print_array(int *a, int n)
{
    for (int i = 0; i < n; ++i) {
        printf("%d ", a[i]);
    }
    printf("\n");
}

void insert(int *a, int n, int insIndex, insValue)
{
    for (int j = n - 1; j >= insIndex; ++j) {
        a[j + 1] = a[j];
    }
    a[insIndex] = insValue;
}

void binary_search(int *a, int n, int toSearch)
{
    int found = 0;
    int l = 0;
    int r = n - 1;
    while (l <= r) {
        int c = l + (r - l) / 2;
        if (toSearch < a[c]) {
            r = c - 1;
        } else if (toSearch > a[c]) {
            l = c + 1;
        } else {
            found = 1;
        }
    }
    if (!found) {
        insert(a, n, l, toSearch);
    }
}

int main()
{
    srand(time(0));
    int a[LEN];
    printf("使用随机数填充数组：\n");
    rand_array(a, LEN);
    print_array(a, LEN);
    bubble_sort(a, LEN);
    printf("排序过后的数组：\n");
    print_array(a, LEN);
    return 0;
}
```

# P219-T4

```C
#include <stdio.h>

void LeftRotate(int* a, int n, int m)
{
    int j = 0;
    int oldValue = a[0];
    int newValue;
    for (int i = 0; i < n; ++i) {
        int k = (j + m) % n;
        newValue = a[k];
        a[k] = oldValue;
        oldValue = newValue;
        j = k;
    }
}

int main()
{
    int a[100];
    int m, n;
    printf("请输入n: \nn = ");
    scanf("%d", &n);
    printf("请输入m: \nm = ");
    scanf("%d", &m);
    printf("请输入n个数：\n");
    for (int i = 0; i < n; ++i) {
        scanf("%d", a + i);
    }
    printf("经过移动后的数组为：\n");
    for (int i = 0; i < n; ++i) {
        printf("%d ", a[i]);
    }
    printf("\n");
    return 0;
}
```

# P291-T5

```C
#include <stdio.h>

int find_next(int* a, int n, int i)
{
    for (int j = i + 1; j < n; ++j) {
        if (a[j] == 1) {
            return j;
        }
    }
    for (int j = 0; j < i; ++j) {
        if (a[j] == 1) {
            return j;
        }
    }
    return -1;
}

int Search(int* a, int n)
{
    int num = 0;
    int count = 0;
    int j = 0;
    while (count < n - 1) {
        if (num == 2) {
            a[j] = 0;
            num = 0;
            count++;
        } else {
            num++;
        }
        j = find_next(a, n, j);
    }
    return j + 1;
}

int main()
{
    int a[100];
    int n;
    printf("请输入n：\nn = ");
    scanf("%d", &n);
    for (int i = 0; i < n; ++i) {
        a[i] = 1;
    }
    printf("剩下的是第%d个人。\n", Search(a, n));
    return 0;
}
```

# P291-T9

```C
#include <stdio.h>

void Trans(int (*a)[3])
{
    for (int i = 1; i < 3; ++i) {
        for (int j = 0; j < i; ++j) {
            int tmp = a[i][j];
            a[i][j] = a[j][i];
            a[j][i] = tmp;
        }
    }
}

int main()
{
    int a[3][3];
    printf("请输入3x3矩阵的9个元素：\n");
    for (int i = 0; i < 3; ++i) {
        for (int j = 0; j < 3; ++j) {
            scanf("%d", &a[i][j]);
        }
    }
    Trans(a);
    printf("转置后：\n");
    for (int i = 0; i < 3; ++i) {
        for (int j = 0; j < 3; ++j) {
            printf("%d ", a[i][j]);
        }
        printf("\n");
    }
    return 0;
}
```