golang力扣leetcode 2055.蜡烛之间的盘子

package main
func platesBetweenCandles(s string, queries [][]int) (ans []int) {
  n := len(s)
  preSum := make([]int, n)
  left := make([]int, n)
  right := make([]int, n)
  sum, l, r := 0, -1, -1
  for i := 0; i < n; i++ {
    if s[i] == '*' {
      sum++
    } else if s[i] == '|' {
      l = i
    }
    //统计该位置i为止一共出现了几次*
    preSum[i] = sum
    //统计该位置i左侧出现|的下标
    left[i] = l
  }
  for i := n - 1; i >= 0; i-- {
    if s[i] == '|' {
      r = i
    }
    //统计该位置i右侧出现|的下标
    right[i] = r
  }
  for _, v := range queries {
    lPoint, rPoint := v[0], v[1]
    //获得左端点右侧的第一个| ， 右端点左侧第一个 | 的下标
    targetIdxL, targetIdxR := right[lPoint], left[rPoint]
    if targetIdxL >= 0 && targetIdxR >= 0 && targetIdxL < targetIdxR {
      ans = append(ans, preSum[targetIdxR]-preSum[targetIdxL])
    } else {
      ans = append(ans, 0)
    }
  }
  return
}