day3

4. [0209长度最小的子数组]

   class Solution {
       public int minSubArrayLen(int target, int[] nums) {
           int numsLength = nums.length;
           for (int k = 0; k <= numsLength-1; k++){
               int sum = 0;
               int i = 0;
               int j = i + k;
               while (j <= numsLength-1){
                   for(int temp = i; temp <= j; temp++){
                       sum = sum + nums[temp];
                   }      
                   if (sum >= target)
                       return k+1; 
                   i++;
                   j++;
               }
           }
           return 0;
       }
   }
   

   • 确实看到提示说是用滑动窗口代替两个for循环，但调节滑动窗口的起始位置这部分精髓代码比较蒙''''''''''

   class Solution {
       public int minSubArrayLen(int target, int[] nums) {
           int numsLength = nums.length; 
           int i = 0; 
           int sum = 0;
           for (int j = 0; j <= numsLength-1; j++){
               sum += nums[j] 
               if (sum >= target){
                   i ++;
                   sum = sum - nums[i-1];  
               }
           }        
           }
           return 0;
       }
   }
   

   • 窗口可能大小subLength，窗口实际大小result，都还没定义出来

   class Solution {
       public int minSubArrayLen(int target, int[] nums) {
           int numsLength = nums.length; 
           int result = Integer.MAX_VALUE;
           int subLength = 0;
           int i = 0; 
           int sum = 0;
           for (int j = 0; j <= numsLength-1; j++){
               sum += nums[j]; 
               while (sum >= target){                
                   subLength = ( j - i + 1 );
               result = result < subLength ? result : subLength;
               sum = sum - nums[i];  
               i ++;
           }
       }        
       return result == Integer.MAX_VALUE ? 0 : result;
   }
   }
   

• 里层用for和用while完全不一样，for只循环一次，while循环多次
  明天继续:)