solve 76.最小覆盖子串

Author: andavid

zh/76.最小覆盖子串.java

@@ -0,0 +1,76 @@
+/*
+ * @lc app=leetcode.cn id=76 lang=java
+ *
+ * [76] 最小覆盖子串
+ *
+ * https://leetcode-cn.com/problems/minimum-window-substring/description/
+ *
+ * algorithms
+ * Hard (37.77%)
+ * Likes:    636
+ * Dislikes: 0
+ * Total Accepted:    61.7K
+ * Total Submissions: 161.6K
+ * Testcase Example:  '"ADOBECODEBANC"\n"ABC"'
+ *
+ * 给你一个字符串 S、一个字符串 T，请在字符串 S 里面找出：包含 T 所有字符的最小子串。
+ *
+ * 示例：
+ *
+ * 输入: S = "ADOBECODEBANC", T = "ABC"
+ * 输出: "BANC"
+ *
+ * 说明：
+ *
+ *
+ * 如果 S 中不存这样的子串，则返回空字符串 ""。
+ * 如果 S 中存在这样的子串，我们保证它是唯一的答案。
+ *
+ *
+ */
+
+// @lc code=start
+class Solution {
+  public String minWindow(String s, String t) {
+    int[] need = new int[128];
+    int[] window = new int[128];
+    for (char ch : t.toCharArray()) {
+      need[ch]++;
+    }
+
+    int left = 0, right = 0;
+    int count = 0;
+    int start = 0, len = s.length() + 1;
+
+    while (right < s.length()) {
+      char ch = s.charAt(right);
+      right++;
+      if (need[ch] > 0) {
+        window[ch]++;
+        if (window[ch] <= need[ch]) {
+          count++;
+        }
+      }
+
+      while (count == t.length()) {
+        if (right - left < len) {
+          start = left;
+          len = right - left;
+        }
+
+        ch = s.charAt(left);
+        left++;
+        if (need[ch] > 0) {
+          if (window[ch] <= need[ch]) {
+            count--;
+          }
+          window[ch]--;
+        }
+      }
+    }
+
+    return (len > s.length()) ? "" : s.substring(start, start + len);
+  }
+}
+// @lc code=end
+