寻找二维峰值

learing

//寻找行中的最大值
int findRowPeak(int row, int** A, int start, int end)
{
    int peak = 0;
    for (int i = start; i <= end; i++)
        if (A[row][i]>A[row][peak])
            peak = i;
    return peak;
}
//寻找列中最大值
int findColPeak(int col, int** A, int start, int end)
{
    int peak = 0;
    for (int i = start; i <= end; i++)
        if (A[i][col]>A[peak][col])
            peak = i;
    return peak;
}
int findTwoDimPeak(int**a, int n, int m)
{
    //初始化行的二分边界，还有列的二分边界
    int rowmin = 0, rowmax = n - 1, rowmid = rowmax / 2;
    int colmin = 0, colmax = m - 1, colmid = colmax / 2;
    while (rowmin <= rowmax && colmin <= colmax)
    {
        //计算行的二分中点
        rowmid =(rowmax - rowmin)/2+rowmin;
        //找出中间行的最大数
        int rowpeak = findRowPeak(rowmid, a, colmin, colmax);
        //比较最大数与上面和下面的数的大小
        if (rowmid!=rowmax&&a[rowmid][rowpeak] < a[rowmid + 1][rowpeak])
        {
            rowmin = rowmid + 1;
        }
        else if (rowmid!=rowmin&&a[rowmid][rowpeak] < a[rowmid - 1][rowpeak])
        {
            rowmax = rowmid - 1;
        }
        else
            return a[rowmid][rowpeak];
        //计算列的二分中点
        colmid = colmin + ((colmax - colmin) / 2);
        int colpeak = findColPeak(colmid, a, rowmin, rowmax);
        if (a[colpeak][colmid] < a[colpeak][colmid + 1])
        {
            colmin = colmid + 1;
        }
        else if (a[colpeak][colmid] < a[colpeak][colmid - 1])
        {
            colmax = colmid - 1;
        }
        else return a[colpeak][colmid];
    }
    return a[rowmid][colmid];
}