golang力扣leetcode 76.最小覆盖子串

package main
import "math"
func minWindow(s string, t string) string {
  wind := make(map[byte]int)
  need := make(map[byte]int)
  for i := range t {
    need[t[i]]++
  }
  left, right, match, start, end, min := 0, 0, 0, 0, 0, math.MaxInt32
  for right < len(s) {
    c := s[right]
    right++
    if need[c] != 0 {
      wind[c]++
      if wind[c] == need[c] {
        match++
      }
    }
    for match == len(need) {
      if right-left < min {
        min = right - left
        start = left
        end = right
      }
      c = s[left]
      left++
      if need[c] != 0 {
        //可能存在s-->aaaa  t-->a,
        //这里只有当s的最后一个a也被移出窗口的时候
        //匹配数才少了1
        if wind[c] == need[c] {
          match--
        }
        wind[c]--
      }
    }
  }
  if min == math.MaxInt32 {
    return ""
  }
  return s[start:end]
}