3.app

3.cpp

@@ -0,0 +1,40 @@
+#include<algorithm>
+#include<string>
+#include<vector>
+#include <iostream>
+
+using namespace std;
+
+//https://leetcode.com/problems/longest-substring-without-repeating-characters
+//利用滑动窗口做 时间复杂度O(n)
+//char 0-256即可表示，用vector不用unordered_map可以省时间
+//指针j遍历字符串，若从未出现过(不在vector里)，cnt++ && 更新maxCnt
+//若干出现过j指向的字符，则i指针移动到上一个该字符的下一位，继续走j
+class Solution {
+public:
+    int lengthOfLongestSubstring(string s) {
+        vector<int> dict(256, 0);
+        int maxCnt = 0, cnt = 0; //cnt用来记录每个以i为首的窗口的大小
+        for (unsigned int i = 0, j = 0; j < s.length(); j++) {
+            if (dict[s[j]] > 0) {
+                while (s[i] != s[j]) {
+                    dict[s[i++]] = 0;
+                    cnt--;
+                }
+                i++;
+            } else {
+                //不在dict里则更新最大值继续
+                dict[s[j]] = 1;
+                maxCnt = max(maxCnt, ++cnt);
+                //continue;
+            }
+        }
+        return maxCnt; 
+    }
+};
+
+int main () {
+    Solution x;
+    int y = x.lengthOfLongestSubstring("abcabcbb");
+    cout << "a:" << y << endl;
+}