leetcode628

//逻辑分析题目 + 分情况讨论 最大的数据就是若干种情况 依次找全并比较大小即可

class Solution {
public:
    int maximumProduct(vector<int>& nums) {
        sort(nums.begin() , nums.end());
        
        int len = nums.size(); //len = 3的特殊情况
        if(len == 3) return nums[0]*nums[1]*nums[2];
        
//len >= 4情况下 两头的双因子必然其中一个 是取正的
        int maxL = nums[0] * nums[1];
        int maxR = nums[len - 1] * nums[len - 2];
        
        
        
        
        int flag = 0;
        if(maxL < maxR) {
            //Max = max(tepL , tempR);
            flag = 1;
        }
        
        
        if(flag == 0){                // - - ... 
               if(nums[len - 1] > 0)  // - - ... +
                   return maxL * nums[len  - 1];
               else                  //  - - ... - 该数组全负 则最大的（绝对值最小）三个数相乘
                   return maxR * nums[len - 3]; 
        }
        else{                       // + + ... + + || - - ...- + + || - + ... + + || - - ... + + +
            //if(nums[len - 3] >= 0)  
                   return max(maxL * nums[len - 1] , maxR * nums[len - 3]);
            
        }
        
       
       
        
    }
};

//[722,634,-504,-379,163,-613,-842,-578,750,951,-158,30,-238,-392,-487,-797,-157,-374,999,-5,-521,-879,-858,382,626,803,-347,903,-205,57,-342,186,-736,17,83,726,-960,343,-984,937,-758,-122,577,-595,-544,-559,903,-183,192,825,368,-674,57,-959,884,29,-681,-339,582,969,-95,-455,-275,205,-548,79,258,35,233,203,20,-936,878,-868,-458,-882,867,-664,-892,-687,322,844,-745,447,-909,-586,69,-88,88,445,-553,-666,130,-640,-918,-7,-420,-368,250,-786]

//-984 -960       969 999