add

public/c/ch1/compare.c

@@ -0,0 +1,21 @@
+#include <stdio.h>
+#include <time.h>
+
+int main() {
+    long timea, timeb, timec;//clock_t timea;
+    long a = 1LL, b = 100000000LL;
+    long long result1 = 0LL, result2 = 0LL;  
+
+    timea = clock();    
+    for (long long i = a; i <= b; i++) {
+        result1 += i;    
+    }
+    timeb = clock();    
+    printf("累加结果: %lld, 所用时间: %lf 毫秒\n", result1, (double)(timeb - timea) / CLOCKS_PER_SEC * 1000);
+
+    result2 = (a + b) * (b - a + 1) / 2;
+    timec = clock();    
+    printf("高斯结果: %lld, 所用时间: %lf 毫秒\n", result2, (double)(timec - timeb) / CLOCKS_PER_SEC * 1000);    
+ 
+    return 0; 
+}

public/c/ch1/compareall.c

@@ -0,0 +1,33 @@
+#include <stdio.h>
+#include <time.h>
+// 函数声明
+long long sum_leijia(long long a, long long b);
+long long sum_gaosi(long long a, long long b);
+
+int main() {
+    clock_t before, middle, after;
+    long long a = 1LL, b = 100000000LL;
+    long long result1 = 0LL, result2 = 0LL;     
+    before = clock();    
+    result1 = sum_leijia(a, b);
+    middle = clock();    
+    printf("累加计算结果: %lld, 所用时间: %lf 毫秒\n", result1, (double)(middle - before) / CLOCKS_PER_SEC * 1000);
+    
+    // 计算公式方式的和并计时
+    result2 = sum_gaosi(a, b);
+    after = clock();    
+    printf("高斯求和结果: %lld, 所用时间: %lf 毫秒\n", result2, (double)(after - middle) / CLOCKS_PER_SEC * 1000);    
+
+    return 0;
+} 
+long long sum_leijia(long long a, long long b) {
+    long long sum = 0LL;
+    for (long long i = a; i <= b; i++) {
+        sum += i;
+    }
+    return sum;
+}
+ 
+long long sum_gaosi(long long a, long long b) {
+    return (a + b) * (b - a + 1) / 2;
+}

public/c/ch1/first.c

@@ -0,0 +1,16 @@
+#include <stdio.h>   
+// row 表示当前要打印的行号（从1开始），n 表示总行数  
+void printAt(int row, int n) {   
+    if (row > n)  
+        return;  
+    for (int i = 0; i < row; i++)  
+        printf("@");   
+    printf("\n"); // 打印完一行后换行  
+    printAt(row + 1, n);  
+}   
+int main() {  
+    int n = 3; 
+    printAt(1, n);   
+    return 0;  
+}
+