Backtracking is an algorithm that considers searching every possible combination in order to solve an optimization problem. Example eight queens puzzle. The eight queen's puzzle is the problem of placing eight chess queens on an 8×8 chessboard so that no two queens threaten each other. Thus, a solution requires that no two queens share the same row, column, or diagonal.
 196 Two color a map with no more than four colors Given any separation of a plane into contiguous regions, producing a figure called a map, no more than four colors are required to color the regions of the map so that no two adjacent regions have the same color 197 Depth-first recursive search in a tree The depth-first search(DFS) is an algorithm for traversing tree or graph which start from the root node and traverse each branch before backtracking. DFS takes less memory compare than Breadth-first search and not necessary to store all of the child pointers at each level. 198 All permutations of a given string Write a program to print all the possible combination of given string. 199 N-Queen Problem The eight queens puzzle is a problem of placing eight chess queens on an 8 x 8 chessboard so that no two queens threaten each other. Thus, a solution requires that no two queens share the same row, column, or diagonal. 200 Rat in a Maze A Maze is given matrix and Rat start from upper left and should reach to lower right. The Rat starts from source to destination and moves only forward and down direction. 201 Subset Sum Given a set of integers, is there a non-empty subset whose sum is zero?For example, given the set {-7, -3, -2, 5, 8}, the answer is yes because the subset {-3, -2, 5} sums to zero. 202 Hamiltonian Cycle Hamiltonian path is a path in an undirected or directed graph that visits each vertex exactly once. A Hamiltonian cycle is a Hamiltonian path that is a cycle.