zoukankan      html  css  js  c++  java
  • 308. Range Sum Query 2D

    Given a 2D matrix matrix, find the sum of the elements inside the rectangle defined by its upper left corner (row1, col1) and lower right corner (row2, col2).

    Range Sum Query 2D
    The above rectangle (with the red border) is defined by (row1, col1) = (2, 1) and (row2, col2) = (4, 3), which contains sum = 8.

    Example:

    Given matrix = [
      [3, 0, 1, 4, 2],
      [5, 6, 3, 2, 1],
      [1, 2, 0, 1, 5],
      [4, 1, 0, 1, 7],
      [1, 0, 3, 0, 5]
    ]
    
    sumRegion(2, 1, 4, 3) -> 8
    update(3, 2, 2)
    sumRegion(2, 1, 4, 3) -> 10
    

    Note:

    1. The matrix is only modifiable by the update function.
    2. You may assume the number of calls to update and sumRegion function is distributed evenly.
    3. You may assume that row1 ≤ row2 and col1 ≤ col2.

    本题和Range Sum Query-mutable 和Range SumQuery-2D比较类似,方法是两者的结合,二维和一维的思路是差不多的,代码如下:

     1 public class NumMatrix {
     2     int[][] BIT;
     3     int[][] nums;
     4     int m;
     5     int n;
     6     public NumMatrix(int[][] matrix) {
     7         if(matrix==null||matrix.length==0||matrix[0].length==0) return;
     8         m = matrix.length;
     9         n = matrix[0].length;
    10         BIT = new int[m+1][n+1];
    11         nums = new int[m][n];
    12         for(int i=0;i<m;i++){
    13             for(int j=0;j<n;j++){
    14                 update(i,j,matrix[i][j]);
    15             }
    16         }
    17     }
    18     
    19     public void update(int row, int col, int val) {
    20         if(m==0||n==0) return;
    21         int diff = val-nums[row][col];
    22         nums[row][col] = val;
    23         for(int i=row+1;i<=m;i+=(i&-i)){
    24             for(int j=col+1;j<=n;j+=(j&-j)){
    25                 BIT[i][j] +=diff;
    26             }
    27         }
    28     }
    29     
    30     public int sumRegion(int row1, int col1, int row2, int col2) {
    31         if(m==0||n==0) return 0;
    32         return getSum(row2+1,col2+1)-getSum(row1,col2+1)-getSum(row2+1,col1)+getSum(row1,col1);
    33     }
    34     public int getSum(int row,int col){
    35         int sum = 0;
    36         for(int i=row;i>0;i-=(i&-i)){
    37             for(int j=col;j>0;j-=(j&-j)){
    38                 sum+=BIT[i][j];
    39             }
    40         }
    41         return sum;
    42     }
    43 }
    44 
    45 /**
    46  * Your NumMatrix object will be instantiated and called as such:
    47  * NumMatrix obj = new NumMatrix(matrix);
    48  * obj.update(row,col,val);
    49  * int param_2 = obj.sumRegion(row1,col1,row2,col2);
    50  */
  • 相关阅读:
    Mycat分布式数据库&.NET链接mysql
    MySQL安装
    Apache 安装配置及开启PHP模块支持
    XSS MSMQ FASTDFS RABBITMQ
    json表单回填(表单反序列化回填值)
    解决80端口被占用
    Oracle for .net & ServiceStack.OrmLite
    MBTiles 离线地图演示
    Java网络编程TCP程序,服务器和客户机交互流程以及基本操作步骤。
    如何使用和理解java的反射机制
  • 原文地址:https://www.cnblogs.com/codeskiller/p/6499837.html
Copyright © 2011-2022 走看看