5个常见C语言算法

十进制转换为二进制的递归程序

字符串逆置的递归程序

整数数位反序，例如12345->54321

四舍五入程序(考虑正负数)

二分法查找的递归函数

#include

#include

#include

//十进制转换为二进制的递归程序

voidDecimalToBinary(int n)

{

if(n<=0)

{

printf("0"); return;

if(n==1)

{

printf("1"); return;

}

else

{

DecimalToBinary((int)n/2);

printf("%d",n%2);

return;

}

}

//字符串逆置的递归程序

voidInverseString(char *s,int n)

{

if(n<=1) return;

else

{

char ch;

ch= s[0];

s[0]= s[n-1];

s[n-1] = ch;

InverseString(s+1,n-2);

}

}

//整数数位反序12345->54321

intInverseIntBit(int n)

{

int sum = 0;

while(n)

{

sum = sum * 10 + n % 10;

n /= 10;

}

return sum;

}

//四舍五入程序(考虑正负数)：

intRoundDouble(double d)

{

int sign = 0;

sign = (d>0)?1:-1;

double td = d + sign * 0.5;

return (int)td;

}

//二分法查找的递归函数

intBinarySearch(int key,int a[],int low,int high)

{

if(low>high) return 0;

int mid = (low+high)/2;

if(a[mid]>key) return BinarySearch(key,a,low+1,mid-1);

else if(a[mid]return BinarySearch(key,a,mid+1,high-1);

else return 1;

}

voidmain()

{

printf("/nDecimal To Binary(224) = ");

DecimalToBinary(224);

char a[27] = "abcdefghijklmnopqrstuvwxyz";

InverseString(a,26);//这里必须考虑后面的'/0'

printf("/nString Inverse(abcdefghijklmnopqrstuvwxyz) = %s/n",a);

int t = InverseIntBit(123456);

printf("/nInt Inverse 123456 = %d/n",t);

int rd1 = RoundDouble(1.4);

int rd2 = RoundDouble(1.5);

int rd3 = RoundDouble(-1.4);

int rd4 = RoundDouble(-1.5);

printf("/nround(1.4)=%d round(1.5)=%d round(-1.4)=%d round(-1.5)=%d/n",rd1,rd2,rd3,rd4);

int aa[10] = {0,1,2,3,4,5,6,7,8,9};

if(1==BinarySearch(7,aa,0,9)) printf("/nI Find 7 /n");

else printf("/nI Cannot Find 7/n");

if(1==BinarySearch(17,aa,0,9)) printf("/nI Find 17/n");

else printf("/nI Cannot Find 17/n");

getch();

}

结果：

{

printf("0"); return;

}

printf("0"); return;

}

}