C - Sum of Substrings

https://codeforces.com/contest/1691/submission/159034603

Codeforces/1691/C/C.cpp

@@ -0,0 +1,43 @@
+#include <iostream>
+#include <string>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+int t, n, k;
+std::string s;
+
+int main() {
+    std::ios::sync_with_stdio(false);
+    cin.tie(nullptr);
+
+    cin >> t;
+
+    while (t--) {
+        cin >> n >> k >> s;
+
+        auto i = s.find_last_of('1');
+        if (i != std::string::npos && n - i - 1 <= k) {
+            k -= n - i - 1;
+            std::swap(s[n - 1], s[i]);
+        }
+
+        auto j = s.find_first_of('1');
+        if (j != n - 1) {
+            if (j != std::string::npos && j <= k) {
+                std::swap(s[0], s[j]);
+                k -= j;
+            }
+        }
+
+        int ans = 0;
+        for (int i = 1; i < s.size(); i++) {
+            ans += std::stoi(s.substr(i - 1, 2));
+        }
+
+        cout << ans << endl;
+    }
+
+    return 0;
+}