lanqiao3514 字串简写

14lanqiao/test7-1.cpp

@@ -0,0 +1,33 @@
+// lanqiao3514 字串简写(枚举)
+#include<bits/stdc++.h>
+using namespace std;
+#define int long long
+signed main(){
+    int k;
+    string s;
+    char a, b;
+    cin >> k >> s >> a >> b;
+    vector<int> ft, bk;
+    for(int i = 0; i < s.size(); i++){
+        if(a == s[i]) ft.push_back(i);
+    }
+    for(int i = 0; i < s.size(); i++){
+        if(b == s[i]) bk.push_back(i);
+    }
+    int ans = 0;
+    for(int i = 0; i < ft.size(); i++){
+        for(int j = 0; j < bk.size(); j++){
+            if( bk[j] - ft[i] + 1 < k) continue;
+            else{
+                ans += bk.size() - j;   // 1 2 1 1 1
+                break;  // 找到一个符合条件的，直接把后面全加上，然后跳出此次循环
+            }
+        }
+    }
+    cout << ans << endl;
+    return 0;
+}
+/* samples -> 6
+4
+abababdb a b
+*/

14lanqiao/test7-2.cpp

@@ -0,0 +1,21 @@
+// lanqiao3514 字串简写(前缀和优化)
+#include<bits/stdc++.h>
+using namespace std;
+#define int long long
+signed main(){
+    int k;
+    string s;
+    char a, b;
+    cin >> k >> s >> a >> b;
+    int ft = 0;
+    int bk = 0;
+    for(int i = 0, j = k - 1; j < s.size(); i++, j++){
+        if(s[i] == a) ft++;
+        if(s[j] == b) bk += ft;
+    }
+    cout << bk << endl;
+}
+/* samples -> 6
+4
+abababdb a b
+*/