2 problem

Author: hitzzc

README.md

@@ -219,6 +219,8 @@ Golang solution for leetcode. For each problem, there is a simple *_test.go to t
 #### [301. Remove Invalid Parentheses](https://github.com/hitzzc/go-leetcode/tree/master/remove_invalid_parentheses)
 #### [303. Range Sum Query - Immutable](https://github.com/hitzzc/go-leetcode/tree/master/range_sum_query_immutable)
 #### [304. Range Sum Query 2D - Immutable](https://github.com/hitzzc/go-leetcode/tree/master/range_sum_query_immutable)
+#### [306. Additive Number](https://github.com/hitzzc/go-leetcode/tree/master/additive_number)
+#### [307. Range Sum Query - Mutable](https://github.com/hitzzc/go-leetcode/tree/master/range_sum_query_mutable)
 
 
 

additive_number/additive_number.cpp

@@ -0,0 +1,30 @@
+#include <string>
+using namespace std;
+
+class Solution {
+public:
+    bool isAdditiveNumber(string num) {
+        return DFS(num, 0, 0, 0, 0);
+    }
+
+    bool DFS(string& num, int start, int length, int first, int second) {
+    	if (start == num.size()) {
+    		if (length > 2) return true;
+    		else return false;
+    	}
+    	int current_num = 0;
+    	for (int i = start; i < num.size(); ++i) {
+    	    if (num[start] == '0' && i != start) break;
+    		current_num = 10*current_num + num[i]-'0';
+    		if (length == 0) first = current_num;
+    		else if (length == 1) second = current_num;
+    		else if (current_num != first+second) continue;
+    		else {
+    			first = second;
+    			second = current_num;
+    		}
+    		if (DFS(num, i+1, length+1, first, second)) return true;
+    	}
+    	return false;
+    }
+};

range_sum_query_mutable/range_sum_query_mutable.cpp

@@ -0,0 +1,40 @@
+class NumArray {
+    vector<int> records;
+    vector<int> ori;
+public:
+    NumArray(vector<int> &nums): records(vector<int>(nums.size()+1, 0)), ori(nums) {
+        for (int i = 0; i < nums.size(); ++i) {
+            add(i+1, nums[i]);
+        }
+    }
+
+    void update(int i, int val) {
+        int diff = val - ori[i];
+        ori[i] = val;
+        add(i+1, diff);
+    }
+
+    int sumRange(int i, int j) {
+        return sum(j+1) - sum(i);
+    }
+
+    void add(int x, int diff) {
+        while (x < records.size()) {
+            records[x] += diff;
+            x += lowbit(x);
+        }
+    }
+
+    int sum(int x) {
+        int ret = 0;
+        while (x > 0) {
+            ret += records[x];
+            x -= lowbit(x);
+        }
+        return ret;
+    }
+
+    int lowbit(int n) {
+        return n&-n;
+    }
+};