【实践课内】6.循环结构3

【实践课内】6.循环结构3/7-1 求简单交错序列前N项和.c

@@ -0,0 +1,20 @@
+#include <stdio.h>
+
+int main() {
+    int n;
+    double ans = 0;
+
+    scanf("%d", &n);
+
+    for (int i = 0; i < n; i++) {
+        if (i % 2 == 0) {
+            ans += 1.0 / (1 + 3 * i);
+        } else {
+            ans -= 1.0 / (1 + 3 * i);
+        }
+    }
+
+    printf("sum = %.3lf\n", ans);
+
+    return 0;
+}

【实践课内】6.循环结构3/7-2 21循环-求和2.c

@@ -0,0 +1,22 @@
+#include <math.h>
+#include <stdio.h>
+
+int main() {
+    long long n, ans = 0;
+
+    scanf("%lld", &n);
+
+    for (long long i = 1; i <= (long long)sqrt(n); i++) {
+        if (n % i == 0) {
+            ans += i;
+
+            if (i != n / i) {
+                ans += n / i;
+            }
+        }
+    }
+
+    printf("%lld\n", ans);
+
+    return 0;
+}

【实践课内】6.循环结构3/7-3 个位数.c

@@ -0,0 +1,22 @@
+#include <stdio.h>
+
+int main() {
+    int n;
+
+    scanf("%d", &n);
+
+    while (n >= 10) {
+        int s = 0;
+
+        while (n) {
+            s += n % 10;
+            n /= 10;
+        }
+
+        n = s;
+    }
+
+    printf("%d\n", n);
+
+    return 0;
+}

【实践课内】6.循环结构3/7-4 循环-分数矩阵.c

@@ -0,0 +1,34 @@
+#include <math.h>
+#include <stdio.h>
+
+int main() {
+    int n;
+
+    while (scanf("%d", &n) != EOF, n != 0) {
+        double ans = n;
+
+        for (int i = 2; i <= n; i++) {
+            ans += (double)(n * 2 - 2 * (i - 1)) / (double)i;
+        }
+
+        /*
+        for (int i = 1; i <= n; i++) {
+            // 对角线左侧
+            for (int j = i; j >= 2; j--) {
+                ans += 1.0 / j;
+            }
+
+            ans += 1;
+
+            // 对角线右侧
+            for (int j = 2; j <= n - i + 1; j++) {
+                ans += 1.0 / j;
+            }
+        }
+        */
+
+        printf("%.2lf\n", ans);
+    }
+
+    return 0;
+}

【额外练习】选择结构/7-33 选择-三数排序.c

@@ -0,0 +1,29 @@
+#include <stdio.h>
+
+int main() {
+    int a, b, c;
+
+    scanf("%d%d%d", &a, &b, &c);
+
+    if (a > b) {
+        int temp = a;
+        a = b;
+        b = temp;
+    }
+
+    if (a > c) {
+        int temp = a;
+        a = c;
+        c = temp;
+    }
+
+    if (b > c) {
+        int temp = b;
+        b = c;
+        c = temp;
+    }
+
+    printf("%d %d %d\n", a, b, c);
+
+    return 0;
+}

【额外练习】选择结构/7-34 选择-凯撒密码.c

@@ -0,0 +1,19 @@
+#include <stdio.h>
+
+int main() {
+    char c;
+
+    scanf("%c", &c);
+
+    if (c >= 'a' && c <= 'z') {
+        c += 3;
+        if (c > 'z') c -= 26;
+    } else if (c >= 'A' && c <= 'Z') {
+        c += 3;
+        if (c > 'Z') c -= 26;
+    }
+
+    printf("%c\n", c);
+
+    return 0;
+}

【额外练习】选择结构/7-35 选择-简单的运算Ⅱ.c

@@ -0,0 +1,27 @@
+#include <stdio.h>
+
+int main() {
+    double a, b, c;
+
+    scanf("%lf%lf%lf", &a, &b, &c);
+
+    if (a == 0) {
+        if (b == 0 && c != 0) {
+            printf("0\n");
+        } else {
+            printf("1\n");
+        }
+    } else {
+        double delta = b * b - 4 * a * c;
+
+        if (delta > 0) {
+            printf("2\n");
+        } else if (delta == 0) {
+            printf("1\n");
+        } else {
+            printf("0\n");
+        }
+    }
+
+    return 0;
+}

【额外练习】选择结构/7-36 选择-三角形和圆.c

@@ -0,0 +1,26 @@
+#include <math.h>
+#include <stdio.h>
+
+int main() {
+    double a, b, c, r;
+
+    scanf("%lf%lf%lf%lf", &a, &b, &c, &r);
+
+    double s = (a + b + c) / 2.0;
+
+    if (s <= a || s <= b || s <= c) {
+        printf("No\n");
+        return 0;
+    }
+
+    double area = sqrt(s * (s - a) * (s - b) * (s - c));
+    double inRadius = area / s;
+
+    if (r <= inRadius) {
+        printf("Yes\n");
+    } else {
+        printf("No\n");
+    }
+
+    return 0;
+}

【额外练习】选择结构/7-38 选择-百分制转五分制.c

@@ -0,0 +1,23 @@
+#include <stdio.h>
+
+int main() {
+    int t;
+
+    scanf("%d", &t);
+
+    if (t >= 90 && t <= 100) {
+        printf("A\n");
+    } else if (t >= 80 && t <= 89) {
+        printf("B\n");
+    } else if (t >= 70 && t <= 79) {
+        printf("C\n");
+    } else if (t >= 60 && t <= 69) {
+        printf("D\n");
+    } else if (t >= 0 && t <= 59) {
+        printf("E\n");
+    } else {
+        printf("Score is error!\n");
+    }
+
+    return 0;
+}