add 3 problems

Author: zhuli19901106

exclusive-time-of-functions_1_AC.cpp

@@ -0,0 +1,66 @@
+#include <cstdio>
+#include <stack>
+#include <string>
+#include <vector>
+using std::sscanf;
+using std::stack;
+using std::string;
+using std::vector;
+
+class Solution {
+public:
+    vector<int> exclusiveTime(int n, vector<string>& logs) {
+        vector<int> res(n, 0);
+        stack<int> si, st;
+        int i, t;
+        
+        vector<string> vs;
+        int len;
+        for (string &log: logs) {
+            split(log, vs, ':');
+            sscanf(vs[0].data(), "%d", &i);
+            sscanf(vs[2].data(), "%d", &t);
+            if (vs[1] == "start") {
+                si.push(i);
+                st.push(t);
+            } else if (vs[1] == "end") {
+                t += 1;
+                if (si.top() != i) {
+                    // not supposed to happen
+                    return vector<int>();
+                }
+                len = t - st.top();
+                res[i] += len;
+                si.pop();
+                st.pop();
+                if (!si.empty()) {
+                    res[si.top()] -= len;
+                }
+            }
+        }
+        
+        return res;
+    }
+private:
+    void split(const string &s, vector<string> &vs, char del) {
+        int ls = s.size();
+        int i;
+        string ss;
+        
+        vs.clear();
+        i = 0;
+        while (true) {
+            if (i < ls && s[i] != del) {
+                ss.push_back(s[i]);
+            } else if (ss.size() > 0) {
+                vs.push_back(ss);
+                ss.clear();
+            }
+            if (i < ls) {
+                ++i;
+            } else {
+                break;
+            }
+        }
+    }
+};

maximum-average-subarray-i_1_AC.cpp

@@ -0,0 +1,29 @@
+#include <algorithm>
+#include <vector>
+using std::max;
+using std::vector;
+
+class Solution {
+public:
+    double findMaxAverage(vector<int>& nums, int k) {
+        double sum;
+        int n = nums.size();
+        int i;
+        
+        sum = 0;
+        i = 0;
+        while (i < k) {
+            sum += nums[i];
+            ++i;
+        }
+        
+        double res = sum;
+        while (i < n) {
+            sum += (nums[i] - nums[i - k]);
+            res = max(res, sum);
+            ++i;
+        }
+        
+        return res / k;
+    }
+};

maximum-average-subarray-ii_1_AC.cpp

@@ -0,0 +1,57 @@
+// If the answer is not among variables, try to find them among values.
+#include <algorithm>
+#include <vector>
+using std::max;
+using std::min;
+using std::vector;
+
+class Solution {
+public:
+    double findMaxAverage(vector<int>& nums, int k) {
+        auto &a = nums;
+        int n = a.size();
+        double ll, mm, rr;
+        static const double EPS = 1e-5;
+        
+        ll = mm = a[0];
+        for (auto &x: a) {
+            ll = min<double>(ll, x);
+            rr = max<double>(rr, x);
+        }
+        while (rr - ll > EPS) {
+            mm = ll + (rr - ll) / 2;
+            if (hasLargerAverage(a, k, mm)) {
+                ll = mm;
+            } else {
+                rr = mm;
+            }
+        }
+        return mm;
+    }
+private:
+    bool hasLargerAverage(vector<int> &a, int k, double ave) {
+        int n = a.size();
+        double sum, pref_sum, min_sum;
+        int i;
+        
+        sum = pref_sum = min_sum = 0;
+        i = 0;
+        while (i < k) {
+            sum += a[i] - ave;
+            ++i;
+        }
+        if (sum > 0) {
+            return true;
+        }
+        while (i < n) {
+            sum += a[i] - ave;
+            pref_sum += a[i - k] - ave;
+            min_sum = min(min_sum, pref_sum);
+            if (sum - min_sum > 0) {
+                return true;
+            }
+            ++i;
+        }
+        return false;
+    }
+};