leetcode solutions

Author: haoel

3Sum/3Sum.cpp

@@ -0,0 +1,153 @@
+// Source : https://oj.leetcode.com/problems/3sum/
+// Author : Hao Chen
+// Date   : 2014-07-22
+
+#include <stdio.h>
+#include <iostream>
+#include <vector>
+#include <set>
+#include <algorithm>
+using namespace std;
+
+
+//solution:  http://en.wikipedia.org/wiki/3SUM
+vector<vector<int> > threeSum(vector<int> &num) {
+
+    vector< vector<int> > result;
+
+    sort(num.begin(), num.end());
+
+    int n = num.size();
+
+    for (int i=0; i<n-2; i++) {
+        //skip the duplication
+        if (i>0 && num[i-1]==num[i]) continue;
+        int a = num[i];
+        int low = i+1;
+        int high = n-1;
+        while ( low < high ) {
+            int b = num[low];
+            int c = num[high];
+            if (a+b+c == 0) {
+                //got the soultion
+                vector<int> v;
+                v.push_back(a);
+                v.push_back(b);
+                v.push_back(c);
+                result.push_back(v);
+                // Continue search for all triplet combinations summing to zero.
+                //skip the duplication
+                while(low<n && num[low]==num[low+1]) low++; 
+                while(high>0 && num[high]==num[high-1]) high--; 
+                low++;
+                high--;
+            } else if (a+b+c > 0) {
+                //skip the duplication
+                while(high>0 && num[high]==num[high-1]) high--;
+                high--;
+            } else{
+                //skip the duplication
+                while(low<n && num[low]==num[low+1]) low++;
+                low++;
+            } 
+        }
+    }
+    return result;
+}
+
+//using combination method could meet <<Time Limit Exceeded>> error
+vector<vector<int> > combination(vector<int> &v, int k);
+bool isSumZero(vector<int>& v);
+int sum(vector<int>& v);
+
+vector<vector<int> > threeSum2(vector<int> &num) {
+    vector< vector<int> > result;
+    vector< vector<int> > r = combination(num, 3);
+    for (int i=0; i<r.size(); i++){
+        if (isSumZero(r[i])){
+            result.push_back(r[i]);
+        }
+    }
+    return result;
+}
+
+bool isSumZero(vector<int>& v){
+    return sum(v)==0;
+}
+
+int sum(vector<int>& v){
+    int s=0;
+    for(int i=0; i<v.size(); i++){
+        s += v[i];
+    }
+    return s;
+}
+
+vector<vector<int> > combination(vector<int> &v, int k) {
+
+    vector<vector<int> > result;
+    vector<int> d;
+    int n = v.size();
+    for (int i=0; i<n; i++){
+        d.push_back( (i<k) ? 1 : 0 );
+    }
+
+    //1) from the left, find the [1,0] pattern, change it to [0,1]
+    //2) move all of the 1 before the pattern to the most left side
+    //3) check all of 1 move to the right
+    while(1){
+        vector<int> tmp;
+        for(int x=0; x<n; x++){
+            if (d[x]) tmp.push_back(v[x]);
+        }
+        sort(tmp.begin(), tmp.end());
+        result.push_back(tmp);
+        //step 1), find [1,0] pattern
+        int i;
+        bool found = false;
+        int ones =0;
+        for(i=0; i<n-1; i++){
+
+            if (d[i]==1 && d[i+1]==0){
+                d[i]=0; d[i+1]=1;
+                found = true;
+                //step 2) move all of right 1 to the most left side
+                for (int j=0; j<i; j++){
+                    d[j]=( ones > 0 ) ? 1 : 0;
+                    ones--;
+                }
+                break;
+            }
+            if (d[i]==1) ones++;
+        }
+        if (!found){
+            break;
+        }
+
+    }
+    return result;
+}
+
+
+void printMatrix(vector<vector<int> > &matrix)
+{
+    for(int i=0; i<matrix.size(); i++){
+        printf("{");
+        for(int j=0; j< matrix[i].size(); j++) {
+            printf("%3d ", matrix[i][j]) ;
+        }
+        printf("}\n");
+    }
+    cout << endl;
+}
+
+
+int main()
+{
+    //int a[] = {-1, 0, 1, 2, -1, 1, -4};
+    int a[] = {-1, 1, 1, 1, -1, -1, 0,0,0};
+    vector<int> n(a, a+sizeof(a)/sizeof(int));
+    vector< vector<int> > result = threeSum(n);
+    printMatrix(result);    
+    return 0;
+}

3SumClosest/3SumClosest.cpp

@@ -0,0 +1,70 @@
+// Source : https://oj.leetcode.com/problems/3sum-closest/
+// Author : Hao Chen
+// Date   : 2014-07-03
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <iostream>
+#include <vector>
+#include <set>
+#include <algorithm>
+using namespace std;
+
+#define INT_MAX 2147483647
+//solution:  http://en.wikipedia.org/wiki/3SUM
+int threeSumClosest(vector<int> &num, int target) {
+
+
+    sort(num.begin(), num.end());
+
+    int n = num.size();
+    int distance = INT_MAX; 
+    int result;
+
+    for (int i=0; i<n-2; i++) {
+        //skip the duplication
+        if (i>0 && num[i-1]==num[i]) continue;
+        int a = num[i];
+        int low = i+1;
+        int high = n-1;
+        while ( low < high ) {
+            int b = num[low];
+            int c = num[high];
+            int sum = a+b+c;
+            if (sum - target == 0) {
+                //got the final soultion
+                return target;
+            } else if (sum -target> 0) {
+                if (abs(sum-target) < distance ) {
+                    distance = abs(sum - target); 
+                    result = sum;
+                }
+                //skip the duplication
+                while(high>0 && num[high]==num[high-1]) high--;
+                high--;
+            } else{
+                if (abs(sum-target) < distance) {
+                    distance = abs(sum - target); 
+                    result = sum;
+                }
+                //skip the duplication
+                while(low<n && num[low]==num[low+1]) low++;
+                low++;
+            } 
+        }
+    }
+    return result;
+
+}
+
+
+
+
+int main()
+{
+    int a[] = {-1, 2, 1, -4};
+    vector<int> n(a, a+sizeof(a)/sizeof(int));
+    int target = 1;
+    cout << threeSumClosest(n, target) << endl;
+    return 0;
+}

4Sum/4Sum.cpp

@@ -0,0 +1,104 @@
+// Source : https://oj.leetcode.com/problems/4sum/
+// Author : Hao Chen
+// Date   : 2014-07-03
+
+#include <iostream>
+#include <vector>
+#include <algorithm>
+using namespace std;
+
+vector<vector<int> > threeSum(vector<int> num, int target); 
+
+vector<vector<int> > fourSum(vector<int> &num, int target) {
+    vector< vector<int> > result;
+    if (num.size()<4) return result;
+    sort( num.begin(), num.end() );
+    
+    for(int i=0; i<num.size()-3; i++) {
+        //skip the duplication
+        if (i>0 && num[i-1]==num[i]) continue;
+        vector<int> n(num.begin()+i+1, num.end());
+        vector<vector<int> > ret = threeSum(n, target-num[i]);
+        for(int j=0; j<ret.size(); j++){
+            ret[j].insert(ret[j].begin(), num[i]);
+            result.push_back(ret[j]);
+        }
+    }
+
+    return result; 
+}
+
+vector<vector<int> > threeSum(vector<int> num, int target) {
+
+    vector< vector<int> > result;
+
+    sort(num.begin(), num.end());
+
+    int n = num.size();
+
+    for (int i=0; i<n-2; i++) {
+        //skip the duplication
+        if (i>0 && num[i-1]==num[i]) continue;
+        int a = num[i];
+        int low = i+1;
+        int high = n-1;
+        while ( low < high ) {
+            int b = num[low];
+            int c = num[high];
+            if (a+b+c == target) {
+                //got the soultion
+                vector<int> v;
+                v.push_back(a);
+                v.push_back(b);
+                v.push_back(c);
+                result.push_back(v);
+                // Continue search for all triplet combinations summing to zero.
+                //skip the duplication
+                while(low<n && num[low]==num[low+1]) low++;
+                while(high>0 && num[high]==num[high-1]) high--;
+                low++;
+                high--;
+            } else if (a+b+c > target) {
+                //skip the duplication
+                while(high>0 && num[high]==num[high-1]) high--;
+                high--;
+            } else{
+                //skip the duplication
+                while(low<n && num[low]==num[low+1]) low++;
+                low++;
+            }
+        }
+    }
+    return result;
+}
+
+
+int printMatrix(vector< vector<int> > &vv)
+{
+    for(int i=0; i<vv.size(); i++) {
+        cout << "[";
+        for(int j=0; j<vv[i].size(); j++) {
+            cout << " " << vv[i][j];
+        }
+        cout << "]" << endl;;
+    }
+}
+
+
+int main()
+{
+    int a[] = {1,0,-1,0,-2,2};
+    vector<int> n(a, a+6);
+    int t = 0;
+    vector< vector<int> > v = fourSum(n, t);
+    printMatrix(v);
+
+    n.clear();
+    int b[] = {-1,-5,-5,-3,2,5,0,4};
+    n.insert(n.begin(), b, b+8);
+    t = -7;
+    v = fourSum(n, t);
+    printMatrix(v);
+
+    return 0;
+}