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LEETCODE 1476. Subrectangle Queries 解题思路分析

题目大意:

子矩形查询

请你实现一个类 SubrectangleQueries ,它的构造函数的参数是一个 rows x cols 的矩形(这里用整数矩阵表示),并支持以下两种操作:

  1. updateSubrectangle(int row1, int col1, int row2, int col2, int newValue) 用 newValue 更新以 (row1,col1) 为左上角且以 (row2,col2) 为右下角的子矩形。
  2. getValue(int row, int col) 返回矩形中坐标 (row,col) 的当前值。

示例 1:

输入:
["SubrectangleQueries","getValue","updateSubrectangle","getValue","getValue","updateSubrectangle","getValue","getValue"]
[[[[1,2,1],[4,3,4],[3,2,1],[1,1,1]]],[0,2],[0,0,3,2,5],[0,2],[3,1],[3,0,3,2,10],[3,1],[0,2]]
输出:
[null,1,null,5,5,null,10,5]
解释:
SubrectangleQueries subrectangleQueries = new SubrectangleQueries([[1,2,1],[4,3,4],[3,2,1],[1,1,1]]);
// 初始的 (4x3) 矩形如下:
// 1 2 1
// 4 3 4
// 3 2 1
// 1 1 1
subrectangleQueries.getValue(0, 2); // 返回 1
subrectangleQueries.updateSubrectangle(0, 0, 3, 2, 5);
// 此次更新后矩形变为:
// 5 5 5
// 5 5 5
// 5 5 5
// 5 5 5
subrectangleQueries.getValue(0, 2); // 返回 5
subrectangleQueries.getValue(3, 1); // 返回 5
subrectangleQueries.updateSubrectangle(3, 0, 3, 2, 10);
// 此次更新后矩形变为:
// 5 5 5
// 5 5 5
// 5 5 5
// 10 10 10
subrectangleQueries.getValue(3, 1); // 返回 10
subrectangleQueries.getValue(0, 2); // 返回 5

示例 2:

输入:
["SubrectangleQueries","getValue","updateSubrectangle","getValue","getValue","updateSubrectangle","getValue"]
[[[[1,1,1],[2,2,2],[3,3,3]]],[0,0],[0,0,2,2,100],[0,0],[2,2],[1,1,2,2,20],[2,2]]
输出:
[null,1,null,100,100,null,20]
解释:
SubrectangleQueries subrectangleQueries = new SubrectangleQueries([[1,1,1],[2,2,2],[3,3,3]]);
subrectangleQueries.getValue(0, 0); // 返回 1
subrectangleQueries.updateSubrectangle(0, 0, 2, 2, 100);
subrectangleQueries.getValue(0, 0); // 返回 100
subrectangleQueries.getValue(2, 2); // 返回 100
subrectangleQueries.updateSubrectangle(1, 1, 2, 2, 20);
subrectangleQueries.getValue(2, 2); // 返回 20

提示:

  • 最多有 500 次updateSubrectangle 和 getValue 操作。
  • 1 <= rows, cols <= 100
  • rows == rectangle.length
  • cols == rectangle[i].length
  • 0 <= row1 <= row2 < rows
  • 0 <= col1 <= col2 < cols
  • 1 <= newValue, rectangle[i][j] <= 10^9
  • 0 <= row < rows
  • 0 <= col < cols

如果想查看本题目是哪家公司的面试题,请参考以下免费链接: https://leetcode.jp/problemdetail.php?id=1476

解题思路分析:

说实话这道题出的并没什么亮点,不过既然做了,这里顺便记录一下。

调用updateSubrectangle方法时,我们使用两层循环更新两个点范围内的所有数值。

getValue返回对应坐标的数值。

实现代码:

int[][] rec;
public SubrectangleQueries(int[][] rectangle) {
    rec=rectangle;
}

public void updateSubrectangle(int row1, int col1, int row2, int col2, int newValue) {
    for(int r=row1;r<=row2;r++){
        for(int c=col1;c<=col2;c++){
            rec[r][c]=newValue;
        }
    }
}

public int getValue(int row, int col) {
    return rec[row][col];
}

本题解法执行时间为43ms。

Runtime: 43 ms, faster than 41.26% of Java online submissions for Subrectangle Queries.

Memory Usage: 52.5 MB, less than 50.00% of Java online submissions for Subrectangle Queries.

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