Directions Reduction
In [“NORTH”, “SOUTH”, “EAST”, “WEST”], the direction “NORTH” + “SOUTH” is going north and coming back right away. What a waste of time! Better to do nothing.
The path becomes [“EAST”, “WEST”], now “EAST” and “WEST” annihilate each other, therefore, the final result is [] (nil in Clojure).
In [“NORTH”, “EAST”, “WEST”, “SOUTH”, “WEST”, “WEST”], “NORTH” and “SOUTH” are not directly opposite but they become directly opposite after the reduction of “EAST” and “WEST” so the whole path is reducible to [“WEST”, “WEST”].
Task
Write a function dirReduc which will take an array of strings and returns an array of strings with the needless directions removed (W<->E or S<->N side by side).
| The Haskell version takes a list of directions with data Direction = North | East | West | South. The Clojure version returns nil when the path is reduced to nothing. The Rust version takes a slice of enum Direction {NORTH, SOUTH, EAST, WEST}. |
Examples
dirReduc(["NORTH", "SOUTH", "SOUTH", "EAST", "WEST", "NORTH", "WEST"]) => ["WEST"]
dirReduc(["NORTH", "SOUTH", "SOUTH", "EAST", "WEST", "NORTH"]) => []
reply
function dirReduc(arr){
const vaild = {"NORTH":"SOUTH","SOUTH":"NORTH","EAST":"WEST","WEST":"EAST"};
return arr.reduce(function(dirs, dir){
if(dirs[dirs.length-1]===vaild[dir]){
dirs.pop();
} else {
dirs.push(dir)
}
return dirs
}, [])
}
