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Given an integer array nums, find the sum of the elements between indices i and j (i ≤ j), inclusive.
Example:
Given nums = [-2, 0, 3, -5, 2, -1] sumRange(0, 2) -> 1 sumRange(2, 5) -> -1 sumRange(0, 5) -> -3
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1 class NumArray 2 { 3 public: 4 NumArray(vector<int> &nums) 5 { 6 sums.push_back(0); 7 for (int i = 0; i < nums.size(); i++) 8 { 9 sums.push_back(sums[i] + nums[i]); 10 } 11 } 12 13 int sumRange(int i, int j) 14 { 15 return sums[j + 1] - sums[i]; 16 } 17 private: 18 vector<int> sums; 19 };
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).
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 sumRegion(1, 1, 2, 2) -> 11 sumRegion(1, 2, 2, 4) -> 12
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1 class NumMatrix 2 { 3 public: 4 NumMatrix(vector<vector<int>> &matrix) 5 { 6 unsigned int nrow = matrix.size(); 7 if (nrow == 0) 8 return; 9 unsigned int ncol = matrix[0].size(); 10 11 for (int i = 0; i <= nrow; i++) 12 { 13 vector<int> row(ncol + 1, 0); 14 matsum.push_back(row); 15 } 16 17 for (int i = 0; i < nrow; i++) 18 { 19 for (int j = 0; j < ncol; j++) 20 { 21 matsum[i + 1][j + 1] = matsum[i][j + 1] + matsum[i + 1][j] - matsum[i][j] + matrix[i][j]; 22 } 23 } 24 } 25 26 int sumRegion(int row1, int col1, int row2, int col2) 27 { 28 return matsum[row2 + 1][col2 + 1] - matsum[row2 + 1][col1] - matsum[row1][col2 + 1] + matsum[row1][col1]; 29 } 30 private: 31 vector<vector<int> > matsum; 32 };
[leetcode] 303. Range Sum Query && 304. Range Sum Query 2D - Immutable
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原文地址：http://www.cnblogs.com/ym65536/p/5701508.html
