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剑指 Offer II 013. 二维子矩阵的和
2022-07-07 17:37:00 【瑾怀轩】
给定一个二维矩阵 matrix,以下类型的多个请求:
计算其子矩形范围内元素的总和,该子矩阵的左上角为 (row1, col1) ,右下角为 (row2, col2) 。
实现 NumMatrix 类:
NumMatrix(int[][] matrix) 给定整数矩阵 matrix 进行初始化
int sumRegion(int row1, int col1, int row2, int col2) 返回左上角 (row1, col1) 、右下角 (row2, col2) 的子矩阵的元素总和。
示例 1:
输入:
["NumMatrix","sumRegion","sumRegion","sumRegion"]
[[[[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]]],[2,1,4,3],[1,1,2,2],[1,2,2,4]]
输出:
[null, 8, 11, 12]
解释:
NumMatrix numMatrix = new NumMatrix([[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]]]);
numMatrix.sumRegion(2, 1, 4, 3); // return 8 (红色矩形框的元素总和)
numMatrix.sumRegion(1, 1, 2, 2); // return 11 (绿色矩形框的元素总和)
numMatrix.sumRegion(1, 2, 2, 4); // return 12 (蓝色矩形框的元素总和)
来源:力扣(LeetCode)
链接:https://leetcode.cn/problems/O4NDxx
著作权归领扣网络所有。商业转载请联系官方授权,非商业转载请注明出处。
java:
class NumMatrix {
public int[][] mat;
public NumMatrix(int[][] matrix) {
//给定二维数组,对二维数组进行初始化
// [[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]]]
this.mat = matrix;
}
public int sumRegion(int row1, int col1, int row2, int col2) {
int total = 0;
//求取给定下标的值
for(int i = row1;i <= row2 ; i++){
for(int j = col1;j<=col2;j++){
total += this.mat[i][j];
}
}
return total;
}
}
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