題目:
Given a string, find the length of the longest substring without repeating characters.
Examples:
Given "abcabcbb"
, the answer is "abc"
, which the length is 3.
Given "bbbbb"
, the answer is "b"
, with the length of 1.
Given "pwwkew"
, the answer is "wke"
, with the length of 3. Note that the answer must be a substring, "pwke"
is a subsequence and not a substring.
解答:
//9行實現:dict用來記錄每個字母最後出現的位置
//start用來記錄每個子序列的起始。
//如果發現某個字符發生了重複,那麼我就把start記爲這個字符上一次出現的位置。
int lengthOfLongestSubstring(string s) {
vector<int> dict(256, -1); //定義一個vector叫做dict,內容是256個-1
int maxLen = 0, start = -1; //標尺start
for (int i = 0; i != s.length(); i++) {
if (dict[s[i]] > start) //如果字符串中的字符大於標尺
start = dict[s[i]]; //那麼標尺刷新;
dict[s[i]] = i; //把dict中對應的值改爲i(最後應該是0123456...)
maxLen = max(maxLen, i - start); //max記爲最大的i-標尺
}
return maxLen;
}