题目:
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”).
解决思路:
1. Check if length(s1) == length(s2). If not, return false.
2. Else, concatenate s1 with itself and see whether s2 is substring of the result.
- input: s1 = apple, s2 = pleap ==> apple is a substring of pleappleap
- input: s1 = apple, s2 = ppale ==> apple is not a substring of ppaleppale
源码如下:
#include <iostream> #include <string> using namespace std; bool isSubstring(string s1, string s2){ if(s1.find(s2) != string::npos) return true; else return false; } bool isRotation(string s1, string s2){ if(s1.length() != s2.length() || s1.length()<=0) return false; return isSubstring(s1+s1, s2); } int main(){ string s1 = "apple"; string s2 = "pleap"; cout<<isRotation(s1, s2)<<endl; cout<<string::npos<<endl; return 0; }