整体的思路一样。就是dp这个怎么求没想出来
class NumMatrix {
private int[][] dp;
public NumMatrix(int[][] matrix) {
if (matrix.length == 0 || matrix[0].length == 0) return;
dp = new int[matrix.length + 1][matrix[0].length + 1];
for (int r = 0; r < matrix.length; r++) {
for (int c = 0; c < matrix[0].length; c++) {
dp[r + 1][c + 1] = dp[r + 1][c] + dp[r][c + 1] + matrix[r][c] - dp[r][c];
}
}
}
public int sumRegion(int row1, int col1, int row2, int col2) {
return dp[row2 + 1][col2 + 1] - dp[row1][col2 + 1] - dp[row2 + 1][col1] + dp[row1][col1];
}
}
/**
* Your NumMatrix object will be instantiated and called as such:
* NumMatrix obj = new NumMatrix(matrix);
* int param_1 = obj.sumRegion(row1,col1,row2,col2);
*/