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  • Java实现 LeetCode 85 最大矩形

    85. 最大矩形

    给定一个仅包含 0 和 1 的二维二进制矩阵,找出只包含 1 的最大矩形,并返回其面积。

    示例:

    输入:
    [
    [“1”,“0”,“1”,“0”,“0”],
    [“1”,“0”,“1”,“1”,“1”],
    [“1”,“1”,“1”,“1”,“1”],
    [“1”,“0”,“0”,“1”,“0”]
    ]
    输出: 6

    PS:
    使用单调栈方法求解(同84)

    class Solution {
          public int maximalRectangle(char[][] matrix) {
            if (matrix == null || matrix.length == 0 || matrix[0].length == 0) return 0;
            int[] height = new int[matrix[0].length];
            int globalmax = 0;
            for (int i = 0; i < matrix.length; i++){
                for (int j = 0; j < matrix[0].length; j++){
                    if (matrix[i][j] == '0') height[j] = 0;
                    else height[j]++;
                }
                globalmax = Math.max(globalmax, maxrow(height));
            }
            return globalmax;
        }
        public int maxrow(int[] height){
            Stack<Integer> st = new Stack<>();
            int localmax = 0;
            for (int i = 0; i <= height.length; i++){
                int h = (i == height.length)? 0 : height[i];
                while (!st.isEmpty() && height[st.peek()] >= h){
                    int maxheight = height[st.pop()];
                    int area = st.isEmpty()? i * maxheight : maxheight * (i - st.peek() -1);
                    localmax = Math.max(localmax, area);
                }
                st.push(i);
            }
            return localmax;
        }
    }
    
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  • 原文地址:https://www.cnblogs.com/a1439775520/p/12946829.html
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