74. 搜索二维矩阵

先对行进行二分查找，最后的lowR是第一个大于target所在行的行数，因此target所在行应该在lowR-1，如果lowR=0，由于没有-1行，所以不存在target，要返回false。

特别注意程序中及时return.

class Solution {public boolean searchMatrix(int[][] matrix, int target) {// boolean ans = false;int lowR = 0, highR = matrix.length, lowC = 0, highC = matrix[0].length;while (lowR < highR) {int midR = (lowR + highR) / 2;if (target == matrix[midR][0]) {// ans = true;return true;} else if (target > matrix[midR][0]) {lowR = midR + 1;} else {highR = midR;}}if (lowR == 0) return false;while (lowC < highC) {int midC = (lowC + highC) / 2;if (target == matrix[lowR - 1][midC]) {// ans = true;return true;} else if (target > matrix[lowR - 1][midC]) {lowC = midC + 1;} else {highC = midC;}}return false;}
}