String Permutations

Author: amitbansal7

14.Backtracking/StringPermutations.cpp

@@ -0,0 +1,71 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+void printResult(char result[], int len)
+{
+	for (int i = 0; i < len; i++)
+		printf("%c", result[i]);
+
+	printf("\n");
+}
+
+void Permutation(char c[], int count[], char result[], int depth, int len, int cs)
+{
+	if (depth == len)
+	{
+		printResult(result, len);
+		return;
+	}
+
+	for (int i = 0; i < cs; i++)
+	{
+		if (count[i] != 0)
+		{
+			result[depth] = c[i];
+			count[i]--;
+			Permutation(c, count, result, depth + 1, len, cs);
+			count[i]++;
+		}
+	}
+}
+
+void StringPermutation(char exp[])
+{
+	int l = strlen(exp);
+	map<char, int> cmap;
+	for (int i = 0; exp[i]; i++)
+	{
+		cmap.insert(pair<char, int>(exp[i], 0));
+		map<char, int> ::iterator it;
+
+		it = cmap.find(exp[i]);
+		++it->second;
+
+		cmap.insert(pair<char, int>(exp[i], it->second));
+	}
+	char c[l + 1];
+	int  oc[l + 1];
+
+	int cs = 0;//no of unique characters
+	map<char, int>::iterator it;
+
+	for (it = cmap.begin(); it != cmap.end(); it++)
+	{
+		c[cs] = it->first;
+		oc[cs] = it->second;
+		cs++;
+	}
+
+	char result[l + 1];
+	Permutation(c, oc, result, 0, l, cs);
+}
+
+int main()
+{
+	char exp[1000];
+	cout << "Enter expression : ";
+	cin >> exp;
+
+	StringPermutation(exp);
+	return 0;
+}