LeetCode刷题day011 (Jieky)

LeetCode第11题

/*
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 and n is at least 2.

The above vertical lines are represented by array [1,8,6,2,5,4,8,3,7]. In this case, the max area of water (blue section) the container can contain is 49.

Example 1:
Input: [1,8,6,2,5,4,8,3,7]
Output: 49
*/
import java.lang.*;
import java.util.*;
public class WithMostWater{
     
	
	// non-negative integers
	public static void main(String[] args){
     
		int[] nums1 = {
     1,8,6,2,5,4,8,3,7};
		
		WithMostWater wmw = new WithMostWater();
		int result = wmw.maxArea03(nums1);
		System.out.println(result);
		
		// Random random = new Random();
		// for (int i =0;i<5;i++){
     
			// System.out.println(random.nextInt(2));
		// }
	}
	
	// 简化
	public int maxArea03(int[] height) {
     
		// You may not slant the container and n is at least 2.
		if (height.length < 2) return 0;
		
		// 从两端点开始，长度是最大的，要想面积增大，只有移动段的那根才有可能面积增大
		// 若两端高度相等，分两种情况，他们之间只有一根比他们高，有两根及以上比他们高
		// 只有一根比他们高，则面积不可能在增加
		// 有两根及以上比他们高，则移动其中一根到比他们高的最近一根（一步到位，或者慢慢移）
		int left = 0,right = height.length-1;
		int maxArea = -0;
		// 生成随机整数，不包含上限
		Random random = new Random();
		while(left < right){
     
			int temp = Math.min(height[left],height[right]) * (right - left);
			if (temp > maxArea){
     
				maxArea = temp;
			}
			
			if (height[left] < height[right]){
     
				left++;
			}else{
     
				right--;
			}
		}
		return maxArea;
	}
	
	// 优化
	public int maxArea02(int[] height) {
     
		// You may not slant the container and n is at least 2.
		if (height.length < 2) return 0;
		
		// 从两端点开始，长度是最大的，要想面积增大，只有移动段的那根才有可能面积增大
		// 若两端高度相等，分两种情况，他们之间只有一根比他们高，有两根及以上比他们高
		// 只有一根比他们高，则面积不可能在增加
		// 有两根及以上比他们高，则移动其中一根到比他们高的最近一根（一步到位，或者慢慢移）
		int left = 0,right = height.length-1;
		int maxArea = -0;
		Random random = new Random();
		while(left < right){
     
			int temp = Math.min(height[left],height[right]) * (right - left);
			if (temp > maxArea){
     
				maxArea = temp;
			}
			
			if (height[left] < height[right]){
     
				left++;
			}else if(height[left] > height[right]){
     
				right--;
			}else{
     
				// 这一步其实可以优化掉，但是表意更重要。随机移动一根
				if(random.nextInt(2) == 0){
     
					left++;
				}else{
     
					right--;
				}
			}
		}
		return maxArea;
	}
	
	// 暴力破解
	public int maxArea01(int[] height) {
     
		// You may not slant the container and n is at least 2.
		if (height.length < 2) return 0;
		
		int max = -1;
		int curr = -1;
		for (int i = 0;i < height.length - 1;i++){
     
			for (int j = i + 1;j < height.length;j++){
     
				curr = (j-i) * Math.min(height[i],height[j]);
				if (curr > max){
     
					max = curr;
				}
			}
		}
		
		return max;
	}
}