Create 2055-plates-between-candles.js

Author: everthis

2055-plates-between-candles.js

@@ -0,0 +1,38 @@
+/**
+ * @param {string} s
+ * @param {number[][]} queries
+ * @return {number[]}
+ */
+const platesBetweenCandles = function(s, queries) {
+  const n = s.length,
+    leftCandlePos = Array(n).fill(-1)
+    rightCandlePos = Array(n).fill(-1)
+    candleCnt = Array(n).fill(0)
+  let pos = -1
+  for(let i = 0; i < n; i++) {
+    if(s[i] === '|') pos = i
+    leftCandlePos[i] = pos
+  }
+  pos = -1
+  for(let i = n - 1; i >= 0; i--) {
+    if(s[i] === '|') pos = i
+    rightCandlePos[i] = pos
+  }
+  for(let i = 0, cnt = 0; i < n; i++) {
+    if(s[i] === '|') cnt++
+    candleCnt[i] = cnt
+  }
+
+  const len = queries.length, res = Array(len).fill(0)
+
+  for(let i = 0; i < len; i++) {
+    const [left, right] = queries[i]
+    const leftCandle = rightCandlePos[left], rightCandle = leftCandlePos[right]
+    const delta = rightCandle - leftCandle
+    if(leftCandle !== -1 && rightCandle !== -1 && delta > 1) {
+      res[i] = delta + 1 - (candleCnt[rightCandle] - candleCnt[leftCandle] + 1)
+    }
+  }
+
+  return res
+}