Trapping Rain Water
Given n non-negative integers representing an elevation map where the width of each bar is 1, compute how much water it is able to trap after raining.
For example,
Given [0,1,0,2,1,0,1,3,2,1,2,1], return 6.
思路:某一格所能盛水的量,取决于其两侧的两个最高格中的较低的那个。考虑从两侧往中间遍历,height表示当前储水线,若A[left]>=height && A[right]>=height,则将height设置为min{A[left],A[right]},即提高当前储水线。优先推进储水线较低的一侧。
1 class Solution { 2 public: 3 int trap( int A[], int n ) { 4 if( n <= 2 ) { return 0; } 5 int content = 0; 6 int left = 0, right = n-1, height = 0; 7 while( left <= right ) { 8 if( A[left] < height ) { content += height-A[left]; ++left; continue; } 9 if( A[right] < height ) { content += height-A[right]; --right; continue; } 10 if( A[left] <= A[right] ) { 11 height = A[left]; 12 ++left; 13 } else { 14 height = A[right]; 15 --right; 16 } 17 } 18 return content; 19 } 20 };
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