《Cracking the Coding Interview》——第1章：数组和字符串——题目8

2014-03-18 02:12

题目：判断一个字符串是否由另一个字符串循环移位而成。

解法：首先长度必须相等。然后将第一个串连拼两次，判断第二个串是否在这个连接串中。

代码：

// 1.8 Assume you have a method isSubstring which checks if one word is a substring of another. Given two strings, s1 and s2, write code to check if s2 is a rotation of s1 using only one call to isSubstring (i.e., “waterbottle” is a rotation of “erbottlewat”).
#include <cstdio>
#include <cstring>
using namespace std;

class Solution {
public:
    bool isStringRotation(char *s1, char *s2) {
        if (s1 == nullptr || s2 == nullptr) {
            return false;
        }
        
        int len1, len2;
        
        len1 = strlen(s1);
        len2 = strlen(s2);
        if (len1 != len2) {
            return false;
        }
        
        const int MAXLEN = 1005;
        static char tmp[MAXLEN];
        
        tmp[0] = 0;
        strcat(tmp, s1);
        strcat(tmp, s1);
        return strstr(tmp, s2) != nullptr;
    }
private:
    bool isSubstring(char *haystack, char *needle) {
        if (haystack == nullptr || needle == nullptr) {
            return false;
        }
        
        return strstr(haystack, needle) != nullptr;
    }
};

int main()
{
    char s1[1005];
    char s2[1005];
    Solution sol;
    
    while (scanf("%s%s", s1, s2) == 2) {
        printf("\"%s\" is ", s2);
        if (!sol.isStringRotation(s1, s2)) {
            printf("not ");
        }
        printf("a rotation of \"%s\".\n", s1);
    }
    
    return 0;
}