Create 1885-count-pairs-in-two-arrays.js

Author: everthis

1885-count-pairs-in-two-arrays.js

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+/**
+ * @param {number[]} nums1
+ * @param {number[]} nums2
+ * @return {number}
+ */
+const countPairs = function(nums1, nums2) {
+  const n = nums1.length
+  const arr = Array(n)
+  for(let i = 0; i < n; i++) {
+    arr[i] = nums1[i] - nums2[i]
+  }
+  // console.log(arr)
+  arr.sort((a, b) => a - b)
+   // console.log(arr)
+  let res = 0
+  for(let i = 0; i < n - 1; i++) {
+    const e = arr[i]
+    const target = -e + 1
+    let l = i + 1, r = n
+    while(l < r) {
+      const mid = ((l + r) >> 1)
+      if(valid(mid, target)) r = mid
+      else l = mid + 1
+    }
+    // console.log(l)
+    res += n - l
+  }
+  
+  return res
+  
+  function valid(mid, t) {
+    return arr[mid] >= t
+  }
+};