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剑指 Offer II 009. 乘积小于 K 的子数组

龙驹书房 2022-04-16 阅读 67
c++
class Solution {
public:
    int numSubarrayProductLessThanK(vector<int>& nums, int k) {
        int count = 0;
        int n = nums.size();
        //vector<int> muls(n+1,1);
        //for(int i=1;i<n+1;++i){
        //    muls[i] = muls[i-1]*nums[i-1];
        //}
        int st = 0;
        int ed = st;
        int mul = 1;
        //精简写法
        for(;ed<n;ed++){
            mul*=nums[ed];
            while(st<=ed&&mul>=k){
                mul/=nums[st++];   
            }
            count += st<=ed?ed-st+1:0;
        }
        /*复杂写法,舍弃
        while(st<=ed&&ed<n&&st<n){
            if(mul<k){
                count+=ed-st+1;
                ++ed;
                if(ed<n){
                    mul*=nums[ed];
                }
            }else{
                ++st;
                if(st<n){
                    mul/=nums[st];
                }
            }
        }
        *///前缀和,超出范围,舍弃
        //for(int i=1;i<n+1;++i){
        //    for(int j=0;j<i;++j){
        //        if(muls[i]/muls[j]<k){
        //            count++;
        //        }
        //    }
        //}
        return count;
    }
};
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