Create 3691.Maximum-Total-Subarray-Value-II_v1.cpp

Author: wisdompeak

Binary_Search/3691.Maximum-Total-Subarray-Value-II/3691.Maximum-Total-Subarray-Value-II_v1.cpp

@@ -0,0 +1,65 @@
+using LL = long long;
+class Solution {
+public:
+    long long maxTotalValue(vector<int>& nums, int k) { 
+        int n = nums.size(), K = log2(n) + 1;                
+
+        int mn[50005][35];    memset(mn, 0x3f, sizeof(mn));
+        int mx[50005][35];    memset(mx, 0xcf, sizeof(mx));
+        for (int i = 0; i < n; i++) mn[i][0] = mx[i][0] = nums[i];
+        for (int k = 1; k <= K; k++) {
+            for (int i = 0; i+(1<<k)-1 < n; i++) {
+                mn[i][k] = min(mn[i][k-1], mn[i+(1<<(k-1))][k-1]);
+                mx[i][k] = max(mx[i][k-1], mx[i+(1<<(k-1))][k-1]);
+            }
+        }
+
+        auto GetDiff = [&](int L, int R){
+            int k = log2(R-L+1);
+            return max(mx[L][k], mx[R-(1<<k)+1][k]) - min(mn[L][k], mn[R-(1<<k)+1][k]);
+        };
+
+        auto count_ge = [&](int th) {
+            int count = 0;
+            int j = 0;
+            for (int i=0; i<n; i++) {
+                while (j<n && GetDiff(i,j)<th) j++;
+                count += n-j;
+            }
+            return count;
+        };
+
+        int lo = 0, hi = 2e9;
+        while (lo < hi) {
+            int mid = hi-(hi-lo)/2;
+            if (count_ge(mid) >= k)
+                lo = mid;
+            else
+                hi = mid-1;
+        }
+        LL th = lo;
+
+        LL ret_g = 0;
+        LL count_g = 0;
+        for (int i=0; i<n; i++) {
+            int l = i, r = n-1;
+            while (l<r) {
+                int mid = l+(r-l)/2;
+                if (GetDiff(i,mid)>th)
+                    r = mid;
+                else
+                    l = mid+1;
+            }
+            if (GetDiff(i, r) > th) {
+                count_g += n-r;
+                for (int j=r; j<n; j++)
+                    ret_g += GetDiff(i, j);
+            }                            
+        }
+
+        LL ret = ret_g + th * (k-count_g);
+
+        return ret;
+
+    }
+};