Container With Most Water
Given n non-negative integers a1, a2, ..., an, where each represents a point at coordinate (i, ai). n vertical lines are drawn such that the two endpoints of line i is at (i, ai) and (i, 0). Find two lines, which together with x-axis forms a container, such that the container contains the most water.
Note: You may not slant the container.
思路:
贪心的方法,用left和right分别记录数组的两边,然后哪边小从哪边往里面移动。因为如果另一边的话只可能更小。
简单的证明:
假设一个中间状态时[(i, a), (j, b)],则 j 右边小于a的边和 i 左边 小于b的边都已经遍历过了。若a < b, j 向左移只会更小, j向右移如果是小于a的值则已经遍历,假设有大于a的值(k, c),则a左边一定又有大于c的值(m,d)使得到达j当前的位置(否则按照代码思路,右边指针会停留k在这等待左边指针向右移动到i),也就意味着[(m,d),(k,c)]访问过或者比它更大的结果访问过,而它一定会大于[(i,a),(k,c)],所以也没有必要再尝试这个状态。综上,j不需要动,i向右移动尝试其他组合。
1 int min(int a, int b){ 2 if(a<b) 3 return a; 4 return b; 5 } 6 int maxArea(vector<int> &height) { 7 // Start typing your C/C++ solution below 8 // DO NOT write int main() function 9 int n = height.size(); 10 int left = 0, right = n-1; 11 int max = min(height[left], height[right])*(right-left), tmp; 12 while(left < right){ 13 if(height[left] < height[right]) 14 left++; 15 else 16 right--; 17 tmp = min(height[left], height[right])*(right-left); 18 if(tmp > max) 19 max = tmp; 20 } 21 return max; 22 }