char类型对应整数值范围0~127。

初始化数组应该为：int[] window = new int[128];

滑动窗口Array

class Solution { public String minWindow(String s, String t) { int[] window = new int[128], need = new int[128]; char[] ss = s.toCharArray(), tt = t.toCharArray(); int count = 0, min = ss.length; String res = ""; for (int i = 0; i < tt.length; i++) { need[tt[i]]++; } int i = 0, j = 0; while(j < ss.length) { char c = ss[j]; window[c]++; if (window[c] <= need[c]) count++; while(count == tt.length && i <= j) { if (j - i + 1 <= min){ res = s.substring(i, j + 1); min = j - i + 1; } window[ss[i]]--; if (window[ss[i]] < need[ss[i]]) count--; i++; } j++; } return res; } }

HashMap

class Solution { Map<Character, Integer> ori = new HashMap<Character, Integer>(); Map<Character, Integer> cnt = new HashMap<Character, Integer>(); public String minWindow(String s, String t) { int tLen = t.length(); for (int i = 0; i < tLen; i++) { ori.put(t.charAt(i), ori.getOrDefault(t.charAt(i), 0) + 1); } int l = 0, r = -1; int len = Integer.MAX_VALUE, ansL = -1, ansR = -1; int count = 0; int sLen = s.length(); while (r < sLen - 1) { ++r; if (ori.containsKey(s.charAt(r))) { cnt.put(s.charAt(r), cnt.getOrDefault(s.charAt(r), 0) + 1); if (cnt.get(s.charAt(r)) <= ori.get(s.charAt(r))) { count++; } } while (count == tLen && l <= r) { if (r - l + 1 < len) { len = r - l + 1; ansL = l; ansR = r + 1; } if (ori.containsKey(s.charAt(l))) { cnt.put(s.charAt(l), cnt.getOrDefault(s.charAt(l), 0) - 1); if (cnt.get(s.charAt(l)) < ori.get(s.charAt(l))) { count--; } } ++l; } } return ansL == -1 ? "" : s.substring(ansL, ansR); } }