leetcode

Solution to some Leetcode problems written in C++

git clone git://git.dimitrijedobrota.com/leetcode.git

0304.cpp (854B)

0 class NumMatrix { 1 int n, m; 2 vector<vector<int>> dp; 3 4 public: 5 NumMatrix(vector<vector<int>> &matrix) 6 : n(matrix.size()), m(matrix[0].size()), dp(vector<vector<int>>(n, vector<int>(m, 0))) { 7 for (int i = 0, sum = 0; i < n; i++) 8 sum = dp[i][0] = matrix[i][0] + sum; 9 for (int i = 0, sum = 0; i < m; i++) 10 sum = dp[0][i] = matrix[0][i] + sum; 11 for (int i = 1; i < n; i++) { 12 for (int j = 1; j < m; j++) { 13 dp[i][j] = matrix[i][j] + dp[i - 1][j] + dp[i][j - 1] - dp[i - 1][j - 1]; 14 } 15 } 16 } 17 18 int sumRegion(int x1, int y1, int x2, int y2) { 19 int res = dp[x2][y2]; 20 if (x1 > 0) res -= dp[x1 - 1][y2]; 21 if (y1 > 0) res -= dp[x2][y1 - 1]; 22 if (x1 > 0 && y1 > 0) res += dp[x1 - 1][y1 - 1]; 23 return res; 24 } 25 };