chapter1&&2

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输入r，h，求圆柱体的表面积，保留3位小数

#include <stdio.h>#include <math.h>int main(){const double pi = 4.0 * atan(1.0);double r, h, s1, s2, s;scanf("%lf%lf", &r, &h);s1 = pi*r*r;s2 = 2*pi*r*h;s = s1*2.0 + s2;printf("Area = %.3lf\n", s);return 0;}

%md %0md

#include <stdio.h>int main(){    int n, m;    scanf("%d", &n);    m = (n%10)*100 + (n/10%10)*10 + n/100;    printf("%03d\n", m);    return 0;}

输出所有形如aabb的四位完全平方数

代码1：

#include <stdio.h>#include <math.h>int main(){int a, b, n;double m;for(a = 1; a <= 9; a++)for(b = 0; b <=9; b++){n = a*1100 + b*11;m = sqrt(n);if(floor(m+0.5) == m)printf("%d\n", n);}return 0;}

代码2：

#include <stdio.h>int main(){int x, n, hi, lo;for(x = 1; ; x++){n = x*x;if(n < 1000)continue;if(n > 9999)break;hi = n / 100;lo = n %100;if(hi/10 == hi%10 && lo/10 == lo %10)printf("%d\n", n);}return 0;}

计时函数的应用：

#include <stdio.h>#include <time.h>int main(){const int MOD = 1000000;int i, j, n, S = 0;scanf("%d", &n);for(i = 1; i <= n; i++){int factorial = 1;for(j = 1; j <= i; j++)factorial = (factorial *j % MOD);S = (S + factorial) % MOD;}printf("%d\n", S);printf("Time used = %.2lf\n", (double)clock() / CLOCKS_PER_SEC);return 0;}

define用法：

#include <stdio.h>#define INF 100000000int main(){int x, max = -INF, min = INF, count = 0, s = 0;while(scanf("%d", &x) == 1){count++;s += x;if(x < min)min = x;if(x > max)max = x;}printf("%d %d %.3lf\n", min, max, (double)s/count);return 0;}

重定向的使用：

#define LOCAL#include <stdio.h>#define INF 100000000int main(){#ifdef LOCALfreopen("g:\\in.txt", "r", stdin);freopen("g:\\out.txt", "w", stdout);#endifint x, n = 0, min = INF, max = -INF, s = 0;while(scanf("%d", &x) == 1){s += x;if(x < min)min = x;if(x > max)max = x;n++;}printf("%d %d %.3lf\n", min, max, (double)s/n);return 0;}

64位整数：在gcc、VS2008中是%lld，在win中是%I64d

保留指定位数的小数：

一。%nf 即输出的数字占n位当原数字位数大于n时原样输出，原数字位数小于n时输出数字左端补上空格，比如原数字为a=1.23456；n为4时输出为1.23456，n为9时输出为
（空格空格1.23456）
二。%n.mf 即输出总共占n位其中有m位小数如a=1.23456 用%4.2f输出为1.23如果用
%5,1f输出为123.4即长度为5小数为1！这里也有当原数字长度小于n时左端补空格这个规则！
还有就是当n前面有个负号时即%-nf或%-n.mf时就右端补空格！

#include <stdio.h>int main(){int a, b, c;scanf("%d%d%d", &a, &b, &c);printf("%.*lf\n", c, (double)a/b);return 0;}

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