74. Search a 2D Matrix

基本上就是binary search，我掌握的还是不错的

先确定行，后确定列

public boolean searchMatrix(int[][] matrix, int target) {
if(matrix == null || matrix.length == 0 || matrix[0].length == 0) {
return false;
}
int low = 0;
int high = matrix.length - 1;
while(low <= high) {
int mid = low+(high-low)/2;
if(matrix[mid][0] > target) {
high = mid-1;
} else if(matrix[mid][0] < target) {
low = mid+1;
} else {
return true;
}
}
if(high < 0) {
return false;
}
int l = 0;
int r = matrix[0].length-1;
while(l <= r) {
int mid = l+(r-l)/2;
if(matrix[high][mid] < target) {
l = mid+1;
} else if(matrix[high][mid] > target) {
r = mid-1;
} else {
return true;
}
}
return false;
}

bug记录：

1.high = length - 1.千万不要忘了减一，我上下两次都忘了

2.当比matrix最小里面还小的时候，注意判断，即17-19行