Add C++ solution for day 4(binarysearch924).

Author: Bruce Yang

91algo/daily/day24[2021-10-03] binarySearch924-delete-sublist-to-make-sum-divisible-by-k_presum.cpp

@@ -0,0 +1,42 @@
+#include <iostream>
+#include <vector>
+#include <algorithm>
+#include <unordered_map>
+using namespace std;
+
+int floorMod(const int& a, const int& b)
+{
+    return (a % b + b) % b;
+}	
+int solve(vector<int>& nums, int k) {
+    int allSum = 0;
+    for (int& num : nums)
+        allSum += num;
+
+    allSum = floorMod(allSum, k);
+    unordered_map<int, int> dict; // dict: 某个前缀和%k得到的余数->pos
+    dict[0] = -1;
+
+    int preSum = 0;
+    int minLen = nums.size();
+    for (int i = 0; i < nums.size(); i++) {
+        preSum += nums[i];
+        int mod = floorMod(preSum, k);
+        dict[mod] = i;
+
+        if (dict.count(floorMod(preSum - allSum, k)))
+            minLen = min(minLen, i - dict[floorMod(preSum - allSum, k)]);
+    }
+    return minLen == nums.size() ? -1 : minLen;
+}
+
+// Test
+int main()
+{
+    vector<int> A = {1, 8, 6, 4, 5};
+    int k = 7;
+    auto res = solve(A, k);
+    cout << res << endl;
+
+    return 0;
+}