[pull] master from ankitpriyarup:master

searching.md

@@ -26,7 +26,7 @@ for (int i = 0; i < (1<<n); ++i)
 {
  if (x&1) take(pos);
  pos++;
- x <<= 1;
+ x >>= 1;
  }
  // process permutation
 }
@@ -56,6 +56,37 @@ do
 {
  // Process permutation
 } while(next_permutation(permutation.begin(), permutation.end()));
+
+
+// std implementation of next_permutation
+bool nextPermutation(std::string &s, int n)
+{
+ // Find the largest index `i` such that `s[i-1]` is less than `s[i]`
+ int i = n-1;
+ while (s[i-1] >= s[i])
+{
+ // if `i` is the first index of the string, we are already at the last
+ // possible permutation (string is sorted in reverse order)
+ if (--i == 0){
+ return false;
+ }
+ }
+
+ // If we reach here, substring `s[i…n-1]` is sorted in reverse order.
+ // Find the highest index `j` to the right of index `i` such that `s[j] > s[i-1]`.
+ int j = n-1;
+ while (j > i && s[j] <= s[i-1]){
+ j--;
+ }
+
+ // swap character at index `i-1` with index `j`
+ std::swap(s[i-1], s[j]);
+
+ // Reverse substring `s[i…n-1]`and return true
+ std::reverse (s.begin() + i, s.end());
+
+ return true;
+}
 ```
 
 ## Backtracking