Solution28.h

//
// Author: huanglijun 
// Date  : 2019/6/14
// Desc  : 28. Implement strStr()
//

/*
Implement strStr().

Return the index of the first occurrence of needle in haystack, or -1 if needle is not part of haystack.

Example 1:

Input: haystack = "hello", needle = "ll"
Output: 2
Example 2:

Input: haystack = "aaaaa", needle = "bba"
Output: -1
Clarification:

What should we return when needle is an empty string? This is a great question to ask during an interview.

For the purpose of this problem, we will return 0 when needle is an empty string. This is consistent to C's strstr() and Java's indexOf().
 */

int strStr(string haystack, string needle) {
    int s1 = (int)haystack.size();
    int s2 = (int)needle.size();
    if(s2 <= 0) return 0;
    if(s1 < s2) return -1;

    int index = -1;
    for(int i = 0; i < s1; i++){
        if(s1-i < s2) break;
        bool flag = true;
        for(int j = 0; j < s2; j++){
            if(haystack[i+j] != needle[j]) {
                flag = false;
                break;
            }
        }

        if(flag) {
            index = i;
            break;
        }
    }
    return index;
}

#ifndef TESTCODE_SOLUTION28_H
#define TESTCODE_SOLUTION28_H

#endif //TESTCODE_SOLUTION28_H