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feat: add solutions to lc problem: No.1439
No.1439.Find the Kth Smallest Sum of a Matrix With Sorted Rows
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‎solution/1400-1499/1439.Find the Kth Smallest Sum of a Matrix With Sorted Rows/README.md

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<!-- 这里可写通用的实现逻辑 -->
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**方法一：暴力枚举**
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注意到 $k$ 的值不超过 $200$，我们逐层遍历，每一层最多保留 $k$ 个数，然后与下一层的 $n$ 个数累加，排序。
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最后返回第 $k$ 个数即可。
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时间复杂度 $O(m \times n \times k \times \log (n \times k))$，空间复杂度 $O(n \times k)$。其中 $m$ 和 $n$ 分别是矩阵的行数和列数。
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<!-- tabs:start -->
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### **Python3**
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<!-- 这里可写当前语言的特殊实现逻辑 -->
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```python
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class Solution:
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def kthSmallest(self, mat: List[List[int]], k: int) -> int:
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pre = [0]
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for cur in mat:
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t = [a + b for a in pre for b in cur[:k]]
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t.sort()
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pre = t[:k]
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return pre[k - 1]
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```
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### **Java**
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<!-- 这里可写当前语言的特殊实现逻辑 -->
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```java
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class Solution {
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public int kthSmallest(int[][] mat, int k) {
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int m = mat.length, n = mat[0].length;
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List<Integer> pre = new ArrayList<>(k);
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List<Integer> cur = new ArrayList<>(n * k);
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pre.add(0);
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for (int[] row : mat) {
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cur.clear();
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for (int a : pre) {
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for (int b : row) {
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cur.add(a + b);
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}
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}
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Collections.sort(cur);
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pre.clear();
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for (int i = 0; i < Math.min(k, cur.size()); ++i) {
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pre.add(cur.get(i));
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}
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}
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return pre.get(k - 1);
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}
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}
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```
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### **C++**
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```cpp
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class Solution {
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public:
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int kthSmallest(vector<vector<int>>& mat, int k) {
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int pre[k];
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int cur[mat[0].size() * k];
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memset(pre, 0, sizeof pre);
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int size = 1;
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for (auto& row : mat) {
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int i = 0;
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for (int j = 0; j < size; ++j) {
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for (int& v : row) {
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cur[i++] = pre[j] + v;
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}
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}
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sort(cur, cur + i);
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size = min(i, k);
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for (int j = 0; j < size; ++j) {
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pre[j] = cur[j];
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}
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}
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return pre[k - 1];
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}
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};
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```
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### **Go**
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```go
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func kthSmallest(mat [][]int, k int) int {
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pre := []int{0}
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for _, row := range mat {
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cur := []int{}
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for _, a := range pre {
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for _, b := range row {
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cur = append(cur, a+b)
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}
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}
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sort.Ints(cur)
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pre = cur[:min(k, len(cur))]
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}
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return pre[k-1]
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}
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func min(a, b int) int {
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if a < b {
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return a
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}
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return b
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}
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```
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### **...**

‎solution/1400-1499/1439.Find the Kth Smallest Sum of a Matrix With Sorted Rows/README_EN.md

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### **Python3**
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```python
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class Solution:
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def kthSmallest(self, mat: List[List[int]], k: int) -> int:
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pre = [0]
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for cur in mat:
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t = [a + b for a in pre for b in cur[:k]]
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t.sort()
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pre = t[:k]
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return pre[k - 1]
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```
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### **Java**
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```java
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class Solution {
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public int kthSmallest(int[][] mat, int k) {
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int m = mat.length, n = mat[0].length;
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List<Integer> pre = new ArrayList<>(k);
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List<Integer> cur = new ArrayList<>(n * k);
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pre.add(0);
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for (int[] row : mat) {
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cur.clear();
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for (int a : pre) {
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for (int b : row) {
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cur.add(a + b);
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}
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}
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Collections.sort(cur);
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pre.clear();
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for (int i = 0; i < Math.min(k, cur.size()); ++i) {
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pre.add(cur.get(i));
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}
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}
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return pre.get(k - 1);
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}
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}
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```
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### **C++**
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```cpp
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class Solution {
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public:
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int kthSmallest(vector<vector<int>>& mat, int k) {
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int pre[k];
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int cur[mat[0].size() * k];
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memset(pre, 0, sizeof pre);
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int size = 1;
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for (auto& row : mat) {
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int i = 0;
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for (int j = 0; j < size; ++j) {
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for (int& v : row) {
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cur[i++] = pre[j] + v;
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}
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}
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sort(cur, cur + i);
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size = min(i, k);
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for (int j = 0; j < size; ++j) {
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pre[j] = cur[j];
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}
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}
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return pre[k - 1];
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}
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};
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```
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### **Go**
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```go
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func kthSmallest(mat [][]int, k int) int {
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pre := []int{0}
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for _, row := range mat {
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cur := []int{}
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for _, a := range pre {
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for _, b := range row {
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cur = append(cur, a+b)
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}
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}
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sort.Ints(cur)
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pre = cur[:min(k, len(cur))]
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}
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return pre[k-1]
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}
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func min(a, b int) int {
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if a < b {
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return a
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}
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return b
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}
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```
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### **...**

‎solution/1400-1499/1439.Find the Kth Smallest Sum of a Matrix With Sorted Rows/Solution.cpp

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class Solution {
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public:
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int kthSmallest(vector<vector<int>>& mat, int k) {
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int pre[k];
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int cur[mat[0].size() * k];
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memset(pre, 0, sizeof pre);
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int size = 1;
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for (auto& row : mat) {
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int i = 0;
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for (int j = 0; j < size; ++j) {
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for (int& v : row) {
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cur[i++] = pre[j] + v;
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}
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}
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sort(cur, cur + i);
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size = min(i, k);
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for (int j = 0; j < size; ++j) {
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pre[j] = cur[j];
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}
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}
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return pre[k - 1];
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}
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};

‎solution/1400-1499/1439.Find the Kth Smallest Sum of a Matrix With Sorted Rows/Solution.go

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func kthSmallest(mat [][]int, k int) int {
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pre := []int{0}
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for _, row := range mat {
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cur := []int{}
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for _, a := range pre {
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for _, b := range row {
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cur = append(cur, a+b)
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}
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}
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sort.Ints(cur)
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pre = cur[:min(k, len(cur))]
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}
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return pre[k-1]
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}
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func min(a, b int) int {
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if a < b {
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return a
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}
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return b
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}

‎solution/1400-1499/1439.Find the Kth Smallest Sum of a Matrix With Sorted Rows/Solution.java

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class Solution {
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public int kthSmallest(int[][] mat, int k) {
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int m = mat.length, n = mat[0].length;
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List<Integer> pre = new ArrayList<>(k);
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List<Integer> cur = new ArrayList<>(n * k);
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pre.add(0);
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for (int[] row : mat) {
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cur.clear();
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for (int a : pre) {
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for (int b : row) {
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cur.add(a + b);
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}
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}
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Collections.sort(cur);
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pre.clear();
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for (int i = 0; i < Math.min(k, cur.size()); ++i) {
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pre.add(cur.get(i));
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}
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}
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return pre.get(k - 1);
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}
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}

‎solution/1400-1499/1439.Find the Kth Smallest Sum of a Matrix With Sorted Rows/Solution.py

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class Solution:
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def kthSmallest(self, mat: List[List[int]], k: int) -> int:
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pre = [0]
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for cur in mat:
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t = [a + b for a in pre for b in cur[:k]]
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t.sort()
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pre = t[:k]
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return pre[k - 1]

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