Implement_strStr.cpp

class Solution {
public:
    int strStr(char *haystack, char *needle) {
        int len1 = strlen(haystack);
		int len2 = strlen(needle);
		
		int charStep[256];
		for (int i = 0; i < 256; ++i)
			charStep[i] = -1;
		for (int i = 0; i < len2; ++i)
			charStep[(int)needle[i]] = i;
		
		for (int i = 0; i <= len1 - len2;)
		{
			int j = 0;
			while (j < len2) {
				if (haystack[i] == needle[j]) {
					++i;
					++j;
				} else {
					char* p = haystack + i + len2 - j;
					if (charStep[(int)*p] == -1) {
						i = p - haystack + 1;
					} else {
						i = p - charStep[(int)*p] - haystack;
					}
					break;
				}
			}
			
			if (j == len2) {
				return i - len2;
			}
		}
		
		return -1;
    }
};