Feb_15.cpp

/*
Question:
Given a m * n matrix mat of ones (representing soldiers) and zeros (representing civilians), return the indexes of the k weakest rows in the matrix ordered from the weakest to the strongest.

A row i is weaker than row j, if the number of soldiers in row i is less than the number of soldiers in
 row j, or they have the same number of soldiers but i is less than j. Soldiers are always stand in the frontier of
  a row, that is, always ones may appear first and then zeros.
Example 1:

Input: mat =
[[1,1,0,0,0],
 [1,1,1,1,0],
 [1,0,0,0,0],
 [1,1,0,0,0],
 [1,1,1,1,1]],
k = 3
Output: [2,0,3]
Explanation:
The number of soldiers for each row is:
row 0 -> 2
row 1 -> 4
row 2 -> 1
row 3 -> 2
row 4 -> 5
Rows ordered from the weakest to the strongest are [2,0,3,1,4]
*/
class Solution {
public:
    vector<int> kWeakestRows(vector<vector<int>>& mat, int k)
    {
        multimap<int,int>occ;
        int count=0,i=0;
        for(auto t:mat)
        {
            for(auto e:t)
            {
                if(e==1)
                    count++;
            }
            occ.insert({count,i});
            i++;
            count=0;
        }
        i=0;
        vector<int>v;
        for(auto y:occ)
        {
            if(i>=k)
                break;
            v.push_back(y.second);
            i++;
        }
        return v;
    }
};