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Commit8c3d8d6

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Created and finished 39. Combination Sum and 17. Letter Combinations of a Phone Number
1 parent5c3d533 commit8c3d8d6

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importjava.util.ArrayList;
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importjava.util.List;
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importjava.util.Map;
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classSolution {
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privateMap<Character,String>digitToChar =Map.of(
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'2',"abc",'3',"def",'4',"ghi",'5',"jkl",
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'6',"mno",'7',"pqrs",'8',"tuv",'9',"wxyz");
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publicList<String>letterCombinations(Stringdigits) {
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if (digits.length() ==0) {
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returnnewArrayList();
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}
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List<String>ans =newArrayList();
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Stringcur ="";
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backtrack(digits,ans,cur,0);
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returnans;
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}
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publicvoidbacktrack(Stringdigits,List<String>ans,Stringcur,intindex) {
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if (cur.length() ==digits.length()) {
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ans.add(cur);
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return;
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}elseif (index >=digits.length()) {
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return;
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}else {
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Stringdigit =digitToChar.get(digits.charAt(index));
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for (charc :digit.toCharArray()) {
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backtrack(digits,ans,cur +c,index +1);
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}
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}
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}
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}

‎39-Combination-Sum.java‎

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classSolution {
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publicList<List<Integer>>combinationSum(int[]candidates,inttarget) {
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List<List<Integer>>ans =newArrayList<List<Integer>>();
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List<Integer>cur =newArrayList();
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backtrack(candidates,target,ans,cur,0);
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returnans;
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}
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publicvoidbacktrack(int[]candidates,inttarget,List<List<Integer>>ans,List<Integer>cur,intindex) {
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if (target ==0) {
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ans.add(newArrayList(cur));
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}elseif (target <0 ||index >=candidates.length) {
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return;
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}else {
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cur.add(candidates[index]);
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backtrack(candidates,target -candidates[index],ans,cur,index);
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cur.remove(cur.get(cur.size() -1));
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backtrack(candidates,target,ans,cur,index +1);
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}
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}
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}

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