Leetcode: Implement strStr()

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Implement strStr().

Returns a pointer to the first occurrence of needle in haystack, or null if needle is not part of haystack.

本以为很复杂，没想到brute force一遍就过了。其实这个题有些高级的算法可以应用，such as KMP，不过面试中不太可能出现。

class Solution {public:    char *strStr(char *haystack, char *needle) {        if (haystack == NULL || needle == NULL) {            return NULL;        }                int hsize = 0, nsize = 0;        for (char *tmp = haystack; *tmp != 0; ++tmp) {            ++hsize;        }        for (char *tmp = needle; *tmp != 0; ++tmp) {            ++nsize;        }        if (hsize < nsize) {            return NULL;        }                char *start = NULL;        char *match = NULL;        for (int i = 0; i <= hsize - nsize; ++i) {            start = haystack + i;            match = needle;            while (*match != 0 && *start == *match) {                ++start;                ++match;            }            if (*match == 0) {                return (haystack + i);            }        }                return NULL;    }};

=================第二次=================

class Solution {public:    int strStr(char *haystack, char *needle) {        if (haystack == NULL || needle == NULL) {            return -1;        }                int max_index = strlen(haystack) - strlen(needle);        for (int i = 0; i <= max_index; ++i) {            char *start = haystack + i;            char *target = needle;            while (*target != '\0' && *start == *target) {                ++start;                ++target;            }            if (*target == '\0') {                return i;            }        }                return -1;    }};

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