Create 2106-maximum-fruits-harvested-after-at-most-k-steps.js

Author: everthis

2106-maximum-fruits-harvested-after-at-most-k-steps.js

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+/**
+ * @param {number[][]} fruits
+ * @param {number} startPos
+ * @param {number} k
+ * @return {number}
+ */
+const maxTotalFruits = function(fruits, startPos, k) {
+    let n = fruits.length, { max, min } = Math
+    let pos = fruits.map(([p,a]) => p)
+    const prefix = Array(n).fill(0)
+
+    let curr = 0
+    for (let i = 0; i < n; i++) {
+        curr += fruits[i][1]
+        prefix[i] = curr      
+    }
+
+  function bisect_left(a, x, lo = 0, hi = null) {
+    // >= lower_bound
+    if (lo < 0) throw new Error('lo must be non-negative')
+    if (hi == null) hi = a.length
+    while (lo < hi) {
+      let mid = parseInt((lo + hi) / 2)
+      a[mid] < x ? (lo = mid + 1) : (hi = mid)
+    }
+    return lo
+  }
+    function bisect_right(a, x, lo = 0, hi = null) {
+    // > upper_bound
+    if (lo < 0) throw new Error('lo must be non-negative')
+    if (hi == null) hi = a.length
+    while (lo < hi) {
+      let mid = parseInt((lo + hi) / 2)
+      x < a[mid] ? (hi = mid) : (lo = mid + 1)
+    }
+    return lo
+  }
+    function query(left, right) {
+         left = max(left, 0)
+        right = min(right, 200000)
+        let l = bisect_left(pos, left)
+        let r = bisect_right(pos, right) - 1
+        if (l > r) return 0
+        if (!l) return prefix[r]
+        return prefix[r] - prefix[l - 1]      
+    }
+
+
+    let best = 0
+    let idx = 0
+    for(let right = startPos + k; right > startPos - 1; right -= 2) {
+        let cand = query(startPos - idx, right)
+        best = max(best, cand)
+        idx += 1      
+    }
+
+    idx = 0
+      for(let left = startPos - k; left < startPos + 1; left += 2) {
+                let cand = query(left, startPos + idx)
+        best = max(best, cand)
+        idx += 1
+      }
+
+    return best    
+};
+