feat: add swift implementation to lcof2 problem: No.013

lcof2/剑指 Offer II 013. 二维子矩阵的和/README.md

@@ -254,6 +254,36 @@ class NumMatrix {
  */
 ```
 
+#### Swift
+
+```swift
+class NumMatrix {
+    private var prefixSum: [[Int]]
+
+    init(_ matrix: [[Int]]) {
+        let m = matrix.count
+        let n = matrix[0].count
+        prefixSum = Array(repeating: Array(repeating: 0, count: n + 1), count: m + 1)
+
+        for i in 1...m {
+            for j in 1...n {
+                prefixSum[i][j] = prefixSum[i - 1][j] + prefixSum[i][j - 1] - prefixSum[i - 1][j - 1] + matrix[i - 1][j - 1]
+            }
+        }
+    }
+
+    func sumRegion(_ row1: Int, _ col1: Int, _ row2: Int, _ col2: Int) -> Int {
+        return prefixSum[row2 + 1][col2 + 1] - prefixSum[row2 + 1][col1] - prefixSum[row1][col2 + 1] + prefixSum[row1][col1]
+    }
+}
+
+/**
+ * Your NumMatrix object will be instantiated and called as such:
+ * let obj = NumMatrix(matrix);
+ * let param_1 = obj.sumRegion(row1,col1,row2,col2);
+ */
+```
+
 <!-- tabs:end -->
 
 <!-- solution:end -->

lcof2/剑指 Offer II 013. 二维子矩阵的和/Solution.swift

@@ -0,0 +1,25 @@
+class NumMatrix {
+    private var prefixSum: [[Int]]
+
+    init(_ matrix: [[Int]]) {
+        let m = matrix.count
+        let n = matrix[0].count
+        prefixSum = Array(repeating: Array(repeating: 0, count: n + 1), count: m + 1)
+
+        for i in 1...m {
+            for j in 1...n {
+                prefixSum[i][j] = prefixSum[i - 1][j] + prefixSum[i][j - 1] - prefixSum[i - 1][j - 1] + matrix[i - 1][j - 1]
+            }
+        }
+    }
+
+    func sumRegion(_ row1: Int, _ col1: Int, _ row2: Int, _ col2: Int) -> Int {
+        return prefixSum[row2 + 1][col2 + 1] - prefixSum[row2 + 1][col1] - prefixSum[row1][col2 + 1] + prefixSum[row1][col1]
+    }
+}
+
+/**
+ * Your NumMatrix object will be instantiated and called as such:
+ * let obj = NumMatrix(matrix);
+ * let param_1 = obj.sumRegion(row1,col1,row2,col2);
+ */