solve minimum window substring

Author: sora0319

minimum-window-substring/sora0319.java

@@ -0,0 +1,87 @@
+public class sora0319 {
+    public class Solution {
+        public String minWindow(String s, String t) {
+            if (s.length() < t.length()) return "";
+
+            Map<Character, Integer> tCounts = new HashMap<>();
+            Map<Character, Integer> wCounts = new HashMap<>();
+
+            // tCounts 초기화
+            for (char ch : t.toCharArray()) {
+                if (tCounts.containsKey(ch)) {
+                    tCounts.put(ch, tCounts.get(ch) + 1);
+                } else {
+                    tCounts.put(ch, 1);
+                }
+            }
+
+            int minLow = 0;
+            int minHigh = s.length();
+            int low = 0;
+            boolean found = false;
+
+            for (int high = 0; high < s.length(); high++) {
+                char ch = s.charAt(high);
+                if (wCounts.containsKey(ch)) {
+                    wCounts.put(ch, wCounts.get(ch) + 1);
+                } else {
+                    wCounts.put(ch, 1);
+                }
+
+                while (isExist(wCounts, tCounts)) {
+                    if (high - low < minHigh - minLow) {
+                        minLow = low;
+                        minHigh = high;
+                        found = true;
+                    }
+
+                    char lowChar = s.charAt(low);
+                    if (tCounts.containsKey(lowChar)) {
+                        int count = wCounts.get(lowChar);
+                        if (count == 1) {
+                            wCounts.remove(lowChar);
+                        } else {
+                            wCounts.put(lowChar, count - 1);
+                        }
+                    } else {
+                        if (wCounts.containsKey(lowChar)) {
+                            int count = wCounts.get(lowChar);
+                            if (count == 1) {
+                                wCounts.remove(lowChar);
+                            } else {
+                                wCounts.put(lowChar, count - 1);
+                            }
+                        }
+                    }
+
+                    low++;
+                }
+            }
+
+            if (found) {
+                return s.substring(minLow, minHigh + 1);
+            } else {
+                return "";
+            }
+        }
+
+        private boolean isExist(Map<Character, Integer> window, Map<Character, Integer> target) {
+            for (Map.Entry<Character, Integer> entry : target.entrySet()) {
+                char ch = entry.getKey();
+                int required = entry.getValue();
+
+                if (!window.containsKey(ch)) {
+                    return false;
+                }
+
+                int count = window.get(ch);
+                if (count < required) {
+                    return false;
+                }
+            }
+            return true;
+        }
+    }
+}
+
+