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problems/0377.组合总和Ⅳ.md

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+
+和之前个回溯法的各个总和串起来一波，本题用回溯稳稳的超时
+
+```
+class Solution {
+public:
+    int combinationSum4(vector<int>& nums, int target) {
+        vector<int> dp(target + 1, 0);
+        dp[0] = 1;
+        for (int i = 0; i <= target; i++) {
+            for (int j = 0; j < nums.size(); j++) {
+                if (i - nums[j] >= 0) {
+                    dp[i] += dp[i - nums[j]];
+                }
+            }
+        }
+        return dp[target];
+    }
+};
+```
+
+
+C++测试用例有超过两个树相加超过int的数据
+超限的情况 
+
+
+一些题解会直接用ull  usigned long long
+
+java 也是四个字节，理论上没有差别，可能后台java和C++测试用例不同，bug.....
+```
+class Solution {
+public:
+    int combinationSum4(vector<int>& nums, int target) {
+        vector<int> dp(target + 1, 0);
+        dp[0] = 1;
+        for (int i = 0; i <= target; i++) {
+            for (int num : nums) {
+                if (i - num >= 0 && dp[i] < INT_MAX - dp[i - num]) {
+                    dp[i] += dp[i - num];
+                }
+            }
+        }
+        return dp[target];
+    }
+};
+```