08-14-25

Luogu/P1015 [NOIP 1999 普及组] 回文数.cpp

@@ -0,0 +1,52 @@
+#include <iostream>
+#include <string>
+#include <algorithm>
+using namespace std;
+
+int charToInt(char c) {
+    if (c >= '0' && c <= '9') return c - '0';
+    if (c >= 'A' && c <= 'Z') return c - 'A' + 10;
+    if (c >= 'a' && c <= 'z') return c - 'a' + 10;
+    return 0;
+}
+
+char intToChar(int x) {
+    if (x < 10) return '0' + x;
+    return 'A' + (x - 10);
+}
+
+string add(const string& a, int jz) {
+    string b(a);
+    reverse(b.begin(), b.end());
+    string tmp(a.size() + 1, '0');
+    int carry = 0;
+    for (size_t i = 0; i < a.size(); i++) {
+        int ia = charToInt(a[i]);
+        int ib = charToInt(b[i]);
+        int sum = ia + ib + carry;
+        carry = sum / jz;
+        tmp[i] = intToChar(sum % jz);
+    }
+    if (carry > 0) tmp[a.size()] = intToChar(carry);
+    else tmp.pop_back();
+    return tmp;
+}
+
+bool check(const string& x) {
+    return equal(x.begin(), x.begin() + x.size()/2, x.rbegin());
+}
+
+int main(){
+    int jz;
+    string n;
+    cin >> jz >> n;
+    for (int i = 0; i <= 30; i++) {
+        if (check(n)) {
+            cout << "STEP=" << i << endl;
+            return 0;
+        }
+        n = add(n, jz);
+    }
+    cout << "Impossible!" << endl;
+}
+