codility-solution5.js

/**
Solution for: http://codesnakers.com/projects/5.png
*/
function solution(S, T) {
    // write your code in JavaScript (Node.js 8.9.4)
	if(S===T)	return "EQUAL";
	
	var lenS = S.length;
	var lenT = T.length;
	var diff;
	var swap = [];
	var sortedS = S.split(""), sortedT = T.split("");
	
	var sortFunc = function(x,y){
		return x.charCodeAt(0) - y.charCodeAt(0);
	};
	var diff = function(a1, a2) {

		var a = [], diff = [];

		for (var i = 0; i < a1.length; i++) {
			a[a1[i]] = true;
		}

		for (var i = 0; i < a2.length; i++) {
			if (a[a2[i]]) {
				delete a[a2[i]];
			} else {
				a[a2[i]] = true;
			}
		}

		for (var k in a) {
			diff.push(k);
		}

		return diff.length>1?false:diff[0];
	}
	sortedS = sortedS.sort(sortFunc);
	sortedT = sortedT.sort(sortFunc);
	
	/*swap or replace*/
	if(lenS === lenT){
		diff = 0;
		for(var i=0; i<lenS; i++){
			if(sortedS[i] !== sortedT[i]){
				diff++;
			}
		}
		if(diff>1){
			return "IMPOSSIBLE";
		}
		if(diff === 0){/* SWAP: its an anagram */
			for(var i=0; i<(lenS-1); i++){
				if(S.charAt(i) === T.charAt(i+1) && S.charAt(i+1) === T.charAt(i)){
					swap.push(S.charAt(i)+" "+S.charAt(i+1));
				}
			}
			if(swap.length === 1){
				return "SWAP "+swap[0];
			}else{
				return "IMPOSSIBLE";
			}
		}
		if(diff === 1){/* REPLACE */
			for(var i=0; i<lenS; i++){
				if(S.charAt(i) !== T.charAt(i)){
					return "REPLACE "+S.charAt(i)+" "+T.charAt(i);
				}
			}
		}
	}else if(Math.abs(lenS-lenT) === 1){/* INSERT */
		var insertLetters;
		if(lenS>lenT){
			insertLetters = diff(sortedT, sortedS);
		}else{
			insertLetters = diff(sortedT, sortedS);
		}
		return insertLetters===false?"IMPOSSIBLE":"INSERT " + insertLetters;
	}
	return "IMPOSSIBLE";
}