Practise 21-Jul-2020

Author: sureshmangs

competitive programming/leetcode/2020-June-Challenge/Day-20-Permutation Sequence.cpp

@@ -0,0 +1,67 @@
+The set [1,2,3,...,n] contains a total of n! unique permutations.
+
+By listing and labeling all of the permutations in order, we get the following sequence for n = 3:
+
+"123"
+"132"
+"213"
+"231"
+"312"
+"321"
+Given n and k, return the kth permutation sequence.
+
+Note:
+
+Given n will be between 1 and 9 inclusive.
+Given k will be between 1 and n! inclusive.
+Example 1:
+
+Input: n = 3, k = 3
+Output: "213"
+Example 2:
+
+Input: n = 4, k = 9
+Output: "2314"
+
+
+
+
+
+
+
+
+class Solution {
+public:
+    vector<int> fact, digit;
+
+    void solve(int n, int  k, string &res){
+        if(n==1){
+            res.push_back(digit[0]+'0');
+            return;
+        }
+
+        int index=k/fact[n-1];
+        if((k%fact[n-1])==0) index-=1;     // boundary case
+
+        res.push_back(digit[index]+'0');    // add digit to index
+        digit.erase(digit.begin()+index);    // remove used number
+        k-=fact[n-1]*index;
+        solve(n-1, k, res);
+    }
+
+    string getPermutation(int n, int k) {
+        string res;
+        if(n==0) return res;
+
+        fact.push_back(1);   // 0!=1
+        for(int i=1;i<=n;i++)
+            fact.push_back(fact[i-1]*i);
+
+        for(int i=1;i<=n;i++)
+            digit.push_back(i);
+
+        solve(n, k, res);
+
+        return res;
+    }
+};

competitive programming/leetcode/60. Permutation Sequence.cpp

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+
+The set [1,2,3,...,n] contains a total of n! unique permutations.
+
+By listing and labeling all of the permutations in order, we get the following sequence for n = 3:
+
+"123"
+"132"
+"213"
+"231"
+"312"
+"321"
+Given n and k, return the kth permutation sequence.
+
+Note:
+
+Given n will be between 1 and 9 inclusive.
+Given k will be between 1 and n! inclusive.
+Example 1:
+
+Input: n = 3, k = 3
+Output: "213"
+Example 2:
+
+Input: n = 4, k = 9
+Output: "2314"
+
+
+
+
+
+class Solution {
+public:
+    vector<int> fact, digit;
+
+    void solve(int n, int  k, string &res){
+        if(n==1){
+            res.push_back(digit[0]+'0');
+            return;
+        }
+
+        int index=k/fact[n-1];
+        if((k%fact[n-1])==0) index-=1;     // boundary case
+
+        res.push_back(digit[index]+'0');    // add digit to index
+        digit.erase(digit.begin()+index);    // remove used number
+        k-=fact[n-1]*index;
+        solve(n-1, k, res);
+    }
+
+    string getPermutation(int n, int k) {
+        string res;
+        if(n==0) return res;
+
+        fact.push_back(1);   // 0!=1
+        for(int i=1;i<=n;i++)
+            fact.push_back(fact[i-1]*i);
+
+        for(int i=1;i<=n;i++)
+            digit.push_back(i);
+
+        solve(n, k, res);
+
+        return res;
+    }
+};