找出矩阵中列最大,行最小的元素

suppose a matrix A. find a element x in this matrix,x is the smallest in his line but the biggest in his column. Give codes in C

for each line:
    find the samllest one in this line.
    if it is also the biggest one in his column, return it.
return -1 if not found

#include <stdio.h>

typedef int B[3][3]; 

int foo(B a, int m, int n) //mxn矩阵
{
    int i, j, t, k, p, q; 
    for (i = 0; i < m; i++){
        for(j = 0, t = a[i][0], p = 0; j < n; j++){
            if (a[i][j] < t){
                t = a[i][j]; 
                p = j; 
            }
        }
        for (q = 0, k = a[0][p]; q < m; q++){ //找出第p列最大数k
            if (a[q][p] > k) k = a[q][p]; 
        }

        if (k == t) return t; 
    }

    return -1; // 没找到
}

int main(int argc, const char *argv[])
{
    B a = {
        {1, 2, 3}, 
        {4, 7, 5}, 
        {8, 6, 9}
    }; 
    printf("%d\n", foo(a, 3, 3));
    return 0;
}