leetcode算法题--使子序列的和等于目标的最少操作次数

原题链接：https://leetcode.cn/problems/minimum-operations-to-form-subsequence-with-target-sum/description/

视频讲解：https://www.bilibili.com/video/BV1Em4y1T7Bq?t=1456.1

这题是真的难。。

func minOperations(nums []int, target int) int {s:= 0cnt := [31]int{}for _, num := range nums {s += numcnt[bits.TrailingZeros(uint(num))]++}if s < target {return -1}if s == target {return 0}s = 0 ans := 0 i := 0for 1 << i <= target {s += cnt[i] << i // cnt[i] * (1 << i) mask := 1<<(i+1) - 1if s >= target&mask {// if s >= target&mask > (2 ^ i)// 可以由小于target&mask的数合成i++ continue}ans++// 比如从32(2^5)分到8(2^3), 32 -> 16 -> 8, 需要5-3=2次 for i++; cnt[i] == 0; i++ {ans++}}return ans  
}