@@ -1134,6 +1134,34 @@ func (this *NumArray) SumRange(i int, j int) int {
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11351135<!-- tabs:end -->
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1137+ ## 304. 二维区域和检索 - 矩阵不可变
1138+ 1139+ [ 原题链接] ( https://leetcode-cn.com/problems/range-sum-query-2d-immutable/ )
1140+ 1141+ ### 解法一:二维前缀和
1142+ 1143+ ``` python
1144+ class NumMatrix :
1145+ 1146+ def __init__ (self matrix : List[List[int ]]):
1147+ m = len (matrix)
1148+ n = len (matrix[0 ]) if matrix else 0
1149+ self .sums = [[0 for _ in range (n + 1 )] for _ in range (m + 1 )]
1150+ 1151+ for i in range (m):
1152+ for j in range (n):
1153+ self .sums[i + 1 ][j + 1 ] = self .sums[i][j + 1 ] + self .sums[i + 1 ][j] - self .sums[i][j] + matrix[i][j]
1154+ 1155+ 1156+ def sumRegion (self row1 : int , col1 : int , row2 : int , col2 : int ) -> int :
1157+ return self .sums[row2 + 1 ][col2 + 1 ] - self .sums[row2 + 1 ][col1] - self .sums[row1][col2 + 1 ] + self .sums[row1][col1]
1158+ 1159+ 1160+ # Your NumMatrix object will be instantiated and called as such:
1161+ # obj = NumMatrix(matrix)
1162+ # param_1 = obj.sumRegion(row1,col1,row2,col2)
1163+ ```
1164+ 11371165## 309. 最佳买卖股票时机含冷冻期
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11391167[ 原题链接] ( https://leetcode-cn.com/problems/best-time-to-buy-and-sell-stock-with-cooldown/ )
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