feat: update solutions to lc problem: No.1863 (#4328)

Author: yanglbme

solution/1800-1899/1863.Sum of All Subset XOR Totals/README.md

@@ -286,7 +286,7 @@ public:
     int subsetXORSum(vector<int>& nums) {
         int n = nums.size();
         int ans = 0;
-        function<void(int, int)> dfs = [&](int i, int s) {
+        auto dfs = [&](this auto&& dfs, int i, int s) {
             if (i >= n) {
                 ans += s;
                 return;

solution/1800-1899/1863.Sum of All Subset XOR Totals/README_EN.md

@@ -287,7 +287,7 @@ public:
     int subsetXORSum(vector<int>& nums) {
         int n = nums.size();
         int ans = 0;
-        function<void(int, int)> dfs = [&](int i, int s) {
+        auto dfs = [&](this auto&& dfs, int i, int s) {
             if (i >= n) {
                 ans += s;
                 return;

solution/1800-1899/1863.Sum of All Subset XOR Totals/Solution2.cpp

@@ -3,7 +3,7 @@ class Solution {
     int subsetXORSum(vector<int>& nums) {
         int n = nums.size();
         int ans = 0;
-        function<void(int, int)> dfs = [&](int i, int s) {
+        auto dfs = [&](this auto&& dfs, int i, int s) {
             if (i >= n) {
                 ans += s;
                 return;