js 实现python的SortedList有序集合

小妖6662026-05-12 8:25

力扣（LeetCode）- 327. 区间和的个数（JavaScript）

这题用到了有序集合，但是js没有这种集合总是超时。手动实现如下。

复制代码

// 默认比较器，处理NaN，规则和Python保持一致：NaN比任何数大，两个NaN相等
function defaultCompare(a, b) {
  if (Number.isNaN(a) && Number.isNaN(b)) return 0;
  if (Number.isNaN(a)) return 1;
  if (Number.isNaN(b)) return -1;
  if (a < b) return -1;
  if (a > b) return 1;
  return 0;
}

class SortedList {
    constructor(items = [], options = []) {
        if (options.compare) {
            this.compare = options.compare
        } else {
            this.compare = defaultCompare
        }
        // 内部存储数组，初始就排序
        this._arr = [...items].sort(this.compare);
    }

    bisectLeft(target) {
        let low = 0
        let high = this._arr.length
        while (low < high) {
            const mid = Math.trunc((low + high) / 2)
            if (this.compare(this._arr[mid], target) < 0) {
                low = mid + 1
            } else {
                high = mid
            }
        }
        return low
    }

    bisectRight(target) {
        let low = 0
        let high = this._arr.length
        while (low < high) {
            const mid = Math.trunc((low + high) / 2)
            if (this.compare(this._arr[mid], target) <= 0) {
                low = mid + 1
            } else {
                high = mid
            }
        }
        return low
    }

    add(item) {
        const pos = this.bisectLeft(item);
        this._arr.splice(pos, 0, item);
    }
}

这题解答方法

复制代码

var countRangeSum = function(nums, lower, upper) {
    const len = nums.length;
    let count = 0
    let sum = 0
    const list = new SortedList([0])
    for (let i = 0;i < len;i++) {
        sum += nums[i]
        const left = list.bisectLeft(sum - upper)
        const right = list.bisectRight(sum - lower)
        count += right - left
        list.add(sum)
    }
    return count
};