Create 2055.Plates-Between-Candles.cpp

Author: wisdompeak

Greedy/2055.Plates-Between-Candles/2055.Plates-Between-Candles.cpp

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+class Solution {
+public:
+ vector<int> platesBetweenCandles(string s, vector<vector<int>>& queries) 
+ {
+ int n = s.size();
+ vector<int>presum(n);
+ int count = 0;
+ for (int i=0; i<n; i++)
+ {
+ count += (s[i]=='*');
+ presum[i] = count;
+ }
+ 
+ vector<int>last(n);
+ int t = -1;
+ for (int i=0; i<n; i++)
+ { 
+ if (s[i]=='|')
+ t = i;
+ last[i] = t;
+ }
+ 
+ vector<int>next(n);
+ t = n;
+ for (int i=n-1; i>=0; i--)
+ {
+ if (s[i]=='|')
+ t = i;
+ next[i] = t; 
+ }
+ 
+ vector<int>rets;
+ for (auto q: queries)
+ {
+ int a = q[0], b = q[1];
+ int x = next[a], y = last[b];
+ 
+ if (x<=y && x>=a && y<=b)
+ rets.push_back(presum[y] - presum[x]);
+ else
+ rets.push_back(0);
+ }
+ 
+ return rets;
+ }
+};