Find_a_peak_element.cpp

#include <iostream>
#include <vector>
using namespace std;

class Solution {
public:
    int FindMaxIndex(vector<vector<int>>& mat, int n, int m, int col)
    {
        int maxValue = -1;
        int index = -1;
        for(int i = 0; i < n; i++)
        {
            if(maxValue < mat[i][col])
            {
                maxValue = mat[i][col];
                index = i;
            }                
        }
        return index;
    }
    vector<int> findPeakGrid(vector<vector<int>>& mat) {
        int n = mat.size();
        int m = mat[0].size();
        int low = 0;
        int high = m - 1;
        while(low <= high)
        {
            int mid = (low +high) / 2;
            int maxRowIndex = FindMaxIndex(mat, n, m, mid);
            int left = mid - 1 >= 0 ? mat[maxRowIndex][mid-1] : -1;
            int right = mid + 1 < m ? mat[maxRowIndex][mid+1] : -1;

            if(mat[maxRowIndex][mid] > left && mat[maxRowIndex][mid] > right)
            {
                return {maxRowIndex, mid};
            }
            else if(mat[maxRowIndex][mid] < left)
            {
                high = mid -1;
            }
            else
            {
                low = mid +1;
            }
        }
        return {-1, -1};
    }
};