11. Container With Most Water(头尾双指针）

Given n non-negative integers a₁, a₂, ..., a_n, where each represents a point at coordinate (i, a_i). n vertical lines are drawn such that the two endpoints of line i is at (i, a_i) and (i, 0). Find two lines, which together with x-axis forms a container, such that the container contains the most water.

思路：每次移动矮的那侧的指针，并且只关心比原来高的情况（因为宽度已经减小了，高度必须增高才可能面积变大）

int maxArea(int* height, int heightSize) {
    int start = 0; 
    int end = heightSize-1;
    int ret = 0;
    int maxStart = 0;
    int maxEnd = 0;

    while(start < end){
        if(height[start] < height[end]){
            if(height[start]*(end-start) > ret) ret = height[start]*(end-start);
            while(start<end){
                start++;
                if(height[start] > maxStart){
                    maxStart = height[start];
                    break;
                }
            }
        }
        else{
            if(height[end]*(end-start) > ret) ret = height[end]*(end-start);
            while(start<end) {
                end--;
                if(height[end] > maxEnd){
                    maxEnd = height[end];
                    break;
                }
            }
        }
    }
    
    return ret;
}