add LongestSubstringWithoutRepeatingCharacters.cpp

daiwb · daiwb · commit b81ad16a8d5d · 2013-01-22T14:18:58.000-08:00
diff --git a/LeetCode/LongestSubstringWithoutRepeatingCharacters.cpp b/LeetCode/LongestSubstringWithoutRepeatingCharacters.cpp
@@ -0,0 +1,41 @@
+#include <iostream>
+#include <vector>
+#include <map>
+#include <iterator>
+using namespace std;
+
+class Solution {
+public:
+    int lengthOfLongestSubstring(string s) {
+        int len = s.length();
+        if (len == 0) return 0;
+        vector<int> prev(len);
+        map<char, int> mp;
+        map<char, int>::iterator itr;
+        for (int i = 0; i < len; ++i) {
+            itr = mp.find(s[i]);
+            if (itr == mp.end()) prev[i] = -1;
+            else prev[i] = mp[s[i]];
+            mp[s[i]] = i;
+        }
+        int ret = 1, add = 0;
+        for (int i = len - 1; i >= 0; --i) {
+            int p = prev[i];
+            if (p == -1) {
+                ++add;
+                ret = max(ret, add);
+                continue;
+            }
+            if (i - p + add <= ret) {
+                add = 0;
+                continue;
+            }
+            for (int j = i - 1; j > p; --j) {
+                if (prev[j] > p) p = prev[j];
+            }
+            ret = max(ret, i - p + add);
+            add = 0;
+        }
+        return ret;
+    }
+};
