java - 查找步行道距离之间的高度

Question

我们有一系列高度，代表步行道上的高度。鉴于start/end索引到数组中，返回从 start 开始的遍历的变化总和索引并以 end 结尾指数。例如，高度 {5, 3, 6, 7, 2}和start=2 , end=4产生总和 1 + 5 = 6 。开始结束结束索引都将是数组中的有效索引 start <= end 。

sumHeights({5, 3, 6, 7, 2}, 2, 4) => 6       
sumHeights({5, 3, 6, 7, 2}, 0, 1) => 2       
sumHeights({5, 3, 6, 7, 2}, 0, 4) => 11    

我正在努力解决这个问题，我已经尝试了其中的一部分，但我很困惑，我得到 ArrayIndexOutOfBoundsException .

 public int sumHeights(int[] heights, int start, int end) {        

   int total =0;   
   int difference =0;   
      for(int i=start;i<=end;i++){           
        if(heights[i] > heights[i++]){         
           difference =heights[i] - heights[i++];                  
        }else if(heights[i++] > heights[i]){         
           difference =heights[i++] - heights[i];            
        }   
        total+=difference;   
      }   
   return total;   
 }  

Answer 1

您在循环中增加 i ，因此可能会超出范围:

for(int i=start;i<=end;i++){      // here i might be last valid index, i.e. 4 in your example     
    if(heights[i] > heights[i++]){    //here i might be 5 (because of i++), i.e. you'd get the ArrayIndexOutOfBoundsException     
       difference =heights[i] - heights[i++]; //here i might be 6 (because of another i++), i.e. you'd get the ArrayIndexOutOfBoundsException                 
    }else if(heights[i++] > heights[i]){     //here i might be 5, i.e. you'd get the ArrayIndexOutOfBoundsException    
       difference =heights[i++] - heights[i];            
    }   
    total+=difference;   
  }   

要修复它，请使用:

for(int i=start;i<end;i++){   
int next = i + 1;     
    if(heights[i] > heights[next]){  
       difference =heights[i] - heights[next]; //assuming you mean next = i + 1 here and not next = i + 2 like in your code               
    }else if(heights[next] > heights[i]){    
       difference =heights[next] - heights[i];            
    }   
    else {
      difference = 0; //due to public demand I'll help you with this, too
    }

    total+=difference;   
  }   

编辑:您还可以使循环更简单:

for(int i=start;i<end;i++){   
  total += Math.abs(heights[i] - heights[i+1]);  
}