第七和第八次

source/_posts/answer8.md

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+---
+title: 第八次作业（答案）
+date: 2020-12-08 16:29:01
+tags:
+---
+
+# P292-10
+
+```C
+#include <stdio.h>
+
+void swap(int array[], int i, int j)
+{
+    int tmp = array[i];
+    array[i] = array[j];
+    array[j] = tmp;
+}
+
+int main(void)
+{
+    int mat[5][5];
+    printf("请输入5x5矩阵的25个元素：\n");
+    for (int i = 0; i < 5; ++i) {
+        for (int j = 0; j < 5; ++j) {
+            scanf("%d", &mat[i][j]);
+        }
+    }
+    int* array = *mat;
+    for (int i = 0; i < 4; ++i) {
+        int min = array[0];
+        for (int j = i + 1; j < 25; ++j) {
+            if (array[j] < array[i]) {
+                swap(array, i, j);
+            }
+        }
+    }
+    int max = array[5];
+    for (int i = 4; i < 25; ++i) {
+        if (array[i] > max) {
+            max = array[i];
+        }
+    }
+    printf("%5d     %5d\n     %5d     \n%5d     %5d\n", array[0], array[1], max, array[2], array[3]);
+    return 0;
+}
+```
+
+# P292-12
+
+```C
+#include <stdio.h>
+#include <string.h>
+
+void sort_str(char* str[], int n)
+{
+    for (int i = 0; i < n - 1; ++i) {
+        int done = 1;
+        for (int j = 0; j < n - i - 1; ++j) {
+            if (strcmp(str[j], str[j + 1]) > 0) {
+                char* tmp = str[j + 1];
+                str[j + 1] = str[j];
+                str[j] = tmp;
+                done = 0;
+            }
+        }
+        if (done) {
+            break;
+        }
+    }
+}
+
+int main(void)
+{
+    char inputs[5][100];
+    for (int i = 0; i < 5; ++i) {
+        fgets(inputs[i], 100, stdin);
+    }
+    char* str[5];
+    for (int i = 0; i < 5; ++i) {
+        str[i] = inputs[i];
+    }
+    sort_str(str, 5);
+    for (int i = 0; i < 5; ++i) {
+        printf("%s", str[i]);
+    }
+    return 0;
+}
+```
+
+# P292-14
+
+```C
+#include <stdio.h>
+
+void reverse(int n)
+{
+    int m;
+    scanf("%d", &m);
+    if (n > 1) {
+        reverse(n - 1);
+    }
+    printf("%d ", m);
+}
+
+int main(void)
+{
+    printf("请问几个数？\nn = ");
+    int n;
+    scanf("%d", &n);
+    printf("请依次输入这些数：\n");
+    reverse(n);
+    printf("\n");
+    return 0;
+}
+```
+
+# P292-17
+
+```C
+#include <stdio.h>
+
+int strcmp(char* p1, char* p2)
+{
+    for (int i = 0;; ++i) {
+        if (p1[i] == '\0') {
+            if (p2[i] == '\0') {
+                return 0;
+            }
+            return -1;
+        }
+        if (p2[i] == '\0') {
+            return 1;
+        }
+        if (p1[i] > p2[i]) {
+            return 1;
+        }
+        if (p1[i] < p2[i]) {
+            return -1;
+        }
+    }
+}
+
+int main(void)
+{
+    char a[100], b[100];
+    fgets(a, 100, stdin);
+    fgets(b, 100, stdin);
+    printf("%d\n", strcmp(a, b));
+    return 0;
+}
+```
+
+# PPT第80页思考题
+
+```C
+#include <stdio.h>
+
+int (*seek(int (*pnt_row)[3]))[3]
+{
+    int i = 0, (*ret_row)[3];
+    ret_row = pnt_row + 1;
+    for (; i < 3; i++) {
+        if (pnt_row[0][i] < 60) {
+            ret_row = pnt_row;
+            break;
+        }
+    }
+    return ret_row;
+}
+
+int main()
+{
+    int grade[3][3] = { { 55, 65, 75 }, { 65, 75, 85 }, { 75, 80, 90 } };
+    int i, j, (*pointer)[3];
+    for (i = 0; i < 3; i++) {
+        pointer = seek(grade + i);
+        if (pointer == grade + i) {
+            printf("No. %d grade list: ", i + 1);
+            for (j = 0; j < 3; j++) {
+                printf("%d ", pointer[0][j]);
+            }
+            printf("\n");
+        }
+    }
+}
+```