第七和第八次

source/_posts/answer7.md

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+---
+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;
+}
+```