PALIN - The Next Palindrome

Author: amitbansal7

SPOJ/PALIN.cpp

@@ -0,0 +1,78 @@
+/* @amitbansal7 */
+#include<bits/stdc++.h>
+using namespace std;
+
+string inc(string left) {
+
+	int idx = left.size() - 1;
+
+	while (left[idx] == '9') {
+		left[idx] = '0';
+		idx--;
+	}
+
+	left[idx] = left[idx] + 1;
+	return left;
+}
+
+int main() {
+	int n;
+	cin >> n;
+
+	while (n--) {
+		string s;
+		cin >> s;
+
+		int len = s.size();
+		bool isOdd = len % 2;
+
+		char center = '\0';
+		if (isOdd) center = s[len / 2];
+
+		string left = s.substr(0, len / 2);
+		string right = left;
+		reverse(right.begin(), right.end());
+
+		string pal = left + center + right;
+		if (center == '\0')
+			pal = left + right;
+		bool res = 0;
+		if (pal > s) {
+			cout << pal << endl;
+		}
+		else {
+			if (center != '\0') {
+				if (center < '9') {
+					center = center + 1;
+					cout << left + center + right << endl;
+					res = 1;
+				}
+				else {
+					center = '0';
+				}
+			}
+			if (res) continue;
+
+			string tLeft;
+			for (int i = 0; i < left.size(); i++)
+				tLeft += '9';
+
+			if (left == tLeft) {
+				string res = "1";
+				for (int i = 0; i < len - 1; i++)
+					res += '0';
+				res += "1";
+				cout << res << endl;
+			} else {
+				left = inc(left);
+				right = left;
+				reverse(right.begin(), right.end());
+
+				if (center == '\0')
+					cout << left + right << endl;
+				else
+					cout << left + center + right << endl;
+			}
+		}
+	}
+}