The C Programming Language 2nd Edition Execise5-4 Answer

Exercise 5-4. Write the function strend(s,t), which returns 1 if the string t occurs at the
end of the string s, and zero otherwise.

简单问题，复习语言。

最直接的想法：

 

//The C Programming Language 2nd Edition Execise5-4 Answer

//by DaNmarner

//http://blog.youkuaiyun.com//DaNmarner

#include<stdio.h>
int strend(char *s,char *t)
{
 char *ps,*pt;
 while (*s != '/0'){
  for(ps = s,pt = t;*ps == *pt;ps++,pt++)
   if(*ps == '/0' || *pt == '/0') break;
  if (*ps == '/0' && *pt == '/0') return 1;
  s++;
 }
 return 0;
}

但其实这个算法效率很低，O(N^2)。下面这个就好多了：

 

//The C Programming Language 2nd Edition Execise5-4 Answer

//by DaNmarner

//http://blog.youkuaiyun.com//DaNmarner

#include<stdio.h>
#include<string.h>
int strend2(char *s,char *t)
{
 int ls = strlen(s);
 int lt = strlen(t);
 if (lt > ls) return 0;
 while(s[--ls] == t[--lt] && lt >= 0);
 if (lt == -1) return 1;
 else return 0;
}

这就是O(n)了~